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How to Write Effective Case Study Conclusions

Table of Contents

Not many people realize that the conclusion is vital to writing your case study. It should summarize the entire study, clarify all the research points, and focus on a few key takeaways.

There are several ways how to write case study conclusion . And we’re here to guide you with some easy and effective steps.

A good conclusion is interesting and captures the essence of your case. It needs to reflect your information and help the reader adopt your conclusion and act on it. Keep reading to learn how to do just that.

Pencils and smartphone on top of books

Importance of Your Case Study Conclusion

Your conclusion is an opportunity for you to summarize your findings and highlight what this study has taught you.

It should also summarize and draw out the main points you’ve discussed and reinforce the importance of your work. Remember, your last impression needs to be just as good as your first. You want to leave readers with something to think about or act on.

Types of Case Studies

Before we proceed on  how to write case study conclusion , let’s take a brief look at the different types of case studies.

There are different types of case studies depending on how they are structured, what is the target audience, and the research methodology used. And your conclusion may vary depending on the nature of the case study.

Some of the most common case studies are:

  • Historical:  Historical events have a multitude of sources offering different perspectives. These perspectives can be applied, compared, and thoroughly analyzed in the modern world.
  • Problem-oriented:  This type of case study is used for solving problems. You can use theoretical situations where you immerse yourself in a situation. Through this, you can thoroughly examine a problem and find ways to resolve it.
  • Cumulative:  In a cumulative study, you gather information and offer comparisons. An example of this is a business case study that tells people about a product’s value.
  • Critical:  Critical case studies focus on exploring the causes and effects of a particular situation. To do this, you can have varying amounts of research and various interviews.
  • Illustrative:  In this case study, certain events are described, as well as the lessons learned.

How to Write Case Study Conclusion Effectively

Writing your conclusion doesn’t need to be complicated. Follow these steps to help you get started on an effective conclusion.

1. Inform the reader precisely why your case study and your findings are relevant

Your conclusion is where you point out the significance of your study. You can cite a specific case in your work and explain how it applies to other relevant cases.

2. Restate your thesis and your main findings

Remind your readers of the thesis statement you made in your introduction but don’t just copy it directly. Also, make sure to mention your main findings to back up your thesis.

3. Give a summary of previous case studies you reviewed

What did you discover that was different about your case? How was previous research helpful? Include this in your conclusion so readers can understand your work and how it contributes to expanding current knowledge.

4. End with recommendations

Wrap up your paper by explaining how your case study and findings could form part of future research on the topic. You can also express your recommendations by commenting on how certain studies, programs, or policies could be improved.

Make sure everything you write in your conclusion section is convincing enough to tell the reader that your case is an effective solution. And if the purpose of your case is complicated, make sure to sum it up in point form. This will help the reader review the case again before approaching the conclusion.

How Long Should Your Conclusion Be?

The length of your conclusion may vary depending on whether you’re writing a thesis or a dissertation. At least 5-9 percent of your overall word count should be dedicated to your conclusion.

Often, empirical scientific studies have brief conclusions describing the main findings and recommendations for future research. On the other hand, humanities topics or systematic reviews may require more space to conclude their analysis. They will need to integrate all the previous sections into an overall argument.

Wrapping Up

Your conclusion is an opportunity to translate and amplify the information you have put in the body of the paper.

More importantly, it is an opportunity to leave a lasting positive impression . Make the right impression by following these quick steps on  how to write case study conclusion  effectively.

How to Write Effective Case Study Conclusions

Abir Ghenaiet

Abir is a data analyst and researcher. Among her interests are artificial intelligence, machine learning, and natural language processing. As a humanitarian and educator, she actively supports women in tech and promotes diversity.

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How to Successfully Conclude a Case Study

Knowing how to successfully conclude a case study is one of the most important parts of every case interview. A strong conclusion shows how well you summarize the entire case solution into a couple of points. In addition, it proves that you can successfully back up your arguments with both quantitative and qualitative facts. It’s also the very last point of the case, thus the point clients remember the most. 

How to Successfully Conclude a Case Study - Best Practice Approaches 

Take approximately 30 seconds before concluding the case, and use this time to jot down key messages you want to touch on during your recommendation. You want to have your ideas sorted out in advance so that you speak clearly and concisely, covering each point without referring back to your notes. 

Practice the art of the elevator pitch

Ideally, your final recommendation should not exceed more than one minute. It is a way to mimic day-to-day interactions with our clients when we are asked to give them key pointers in a short summary. 

Answer first and answer focused

As you will see more in detail with Prepmatter cases, in many case types, you should start with the answer. However, in certain case types where the client has a business problem yet to be diagnosed (e.g., competitive response strategy, profitability, operations), it’s best to start with your diagnosis and then provide recovery solutions. 

Allocate time correctly

Make sure to allocate most of your time to the delivery of a solution and its supporting evidence. Some candidates spend half - if not more - of their time in delivering risks and next steps, which dilutes the key messages in the recommendation. Conclude the case in the following structure: 

  • Recommendation: Give a one-sentence action-oriented recommendation. 
  • First supporting fact with figures (quantitative) 
  • Second supporting fact with figures (quantitative)
  • Third supporting fact (qualitative)
  • Risks: Comment on the potential risks assessed during the case. Try to mention them in a way supporting your conclusion. 
  • Next steps: Provide direction on how they should act going forward based on the recommendation.

Example of a Strong Conclusion

  • I suggest the client should go ahead with this investment and enter the cosmetics market with their new product.
  • With this investment, the client can make an $800M profit over the next three years, which is higher than our objective of $600M. 
  • The cosmetics market is expected to grow at a 9% annual growth rate over the next 10 years, promising sustainable value in the long term. 
  • We can create synergies by combining our back-end operations with our existing business. 
  • Risks: There is a regulatory risk given that the authorities increase their health restrictions related to cosmetics products. The client should make sure that they spend additional effort to comply with all regulations. 
  • Next steps: As the next step, I suggest the client design a detailed production plan for the new product. 

How to Practice Case Conclusions

There are various ways to practice concluding a case. Practice with the Prepmatter cases or any other case you may have. You can change the numbers in the case to create hypothetical facts and draw a new conclusion. By doing so, you can also change the recommendation if the numbers change significantly. For instance, if you change the 3-year profits to $400M from $800M in the example above, the recommendation would change from ‘Go’ to ‘No-go’. 

Knowing how to successfully conclude a case study is a critical part of each case interview, so we recommend you set aside specific time to review it with your coach or case partner. Take time to solve as many cases as possible to improve how well you summarize, support, and present your conclusion.

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The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of the main topics covered or a re-statement of your research problem, but a synthesis of key points and, if applicable, where you recommend new areas for future research. For most college-level research papers, one or two well-developed paragraphs is sufficient for a conclusion, although in some cases, more paragraphs may be required in summarizing key findings and their significance.

Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University.

Importance of a Good Conclusion

A well-written conclusion provides you with important opportunities to demonstrate to the reader your understanding of the research problem. These include:

  • Presenting the last word on the issues you raised in your paper . Just as the introduction gives a first impression to your reader, the conclusion offers a chance to leave a lasting impression. Do this, for example, by highlighting key findings in your analysis that advance new understanding about the research problem, that are unusual or unexpected, or that have important implications applied to practice.
  • Summarizing your thoughts and conveying the larger significance of your study . The conclusion is an opportunity to succinctly re-emphasize  the "So What?" question by placing the study within the context of how your research advances past research about the topic.
  • Identifying how a gap in the literature has been addressed . The conclusion can be where you describe how a previously identified gap in the literature [described in your literature review section] has been filled by your research.
  • Demonstrating the importance of your ideas . Don't be shy. The conclusion offers you the opportunity to elaborate on the impact and significance of your findings. This is particularly important if your study approached examining the research problem from an unusual or innovative perspective.
  • Introducing possible new or expanded ways of thinking about the research problem . This does not refer to introducing new information [which should be avoided], but to offer new insight and creative approaches for framing or contextualizing the research problem based on the results of your study.

Bunton, David. “The Structure of PhD Conclusion Chapters.” Journal of English for Academic Purposes 4 (July 2005): 207–224; Conclusions. The Writing Center. University of North Carolina; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Conclusions. The Writing Lab and The OWL. Purdue University; Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Structure and Writing Style

I.  General Rules

The function of your paper's conclusion is to restate the main argument . It reminds the reader of the strengths of your main argument(s) and reiterates the most important evidence supporting those argument(s). Do this by stating clearly the context, background, and necessity of pursuing the research problem you investigated in relation to an issue, controversy, or a gap found in the literature. Make sure, however, that your conclusion is not simply a repetitive summary of the findings. This reduces the impact of the argument(s) you have developed in your essay.

When writing the conclusion to your paper, follow these general rules:

  • Present your conclusions in clear, simple language. Re-state the purpose of your study, then describe how your findings differ or support those of other studies and why [i.e., what were the unique or new contributions your study made to the overall research about your topic?].
  • Do not simply reiterate your findings or the discussion of your results. Provide a synthesis of arguments presented in the paper to show how these converge to address the research problem and the overall objectives of your study.
  • Indicate opportunities for future research if you haven't already done so in the discussion section of your paper. Highlighting the need for further research provides the reader with evidence that you have an in-depth awareness of the research problem and that further investigations should take place.

Consider the following points to help ensure your conclusion is presented well:

  • If the argument or purpose of your paper is complex, you may need to summarize the argument for your reader.
  • If, prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the end of your paper to describe your main points and explain their significance.
  • Move from a detailed to a general level of consideration that returns the topic to the context provided by the introduction or within a new context that emerges from the data. 

The conclusion also provides a place for you to persuasively and succinctly restate the research problem, given that the reader has now been presented with all the information about the topic . Depending on the discipline you are writing in, the concluding paragraph may contain your reflections on the evidence presented. However, the nature of being introspective about the research you have conducted will depend on the topic and whether your professor wants you to express your observations in this way.

NOTE : If asked to think introspectively about the topics, do not delve into idle speculation. Being introspective means looking within yourself as an author to try and understand an issue more deeply, not to guess at possible outcomes or make up scenarios not supported by the evidence.

II.  Developing a Compelling Conclusion

Although an effective conclusion needs to be clear and succinct, it does not need to be written passively or lack a compelling narrative. Strategies to help you move beyond merely summarizing the key points of your research paper may include any of the following strategies:

  • If your essay deals with a critical, contemporary problem, warn readers of the possible consequences of not attending to the problem proactively.
  • Recommend a specific course or courses of action that, if adopted, could address a specific problem in practice or in the development of new knowledge.
  • Cite a relevant quotation or expert opinion already noted in your paper in order to lend authority and support to the conclusion(s) you have reached [a good place to look is research from your literature review].
  • Explain the consequences of your research in a way that elicits action or demonstrates urgency in seeking change.
  • Restate a key statistic, fact, or visual image to emphasize the most important finding of your paper.
  • If your discipline encourages personal reflection, illustrate your concluding point by drawing from your own life experiences.
  • Return to an anecdote, an example, or a quotation that you presented in your introduction, but add further insight derived from the findings of your study; use your interpretation of results to recast it in new or important ways.
  • Provide a "take-home" message in the form of a succinct, declarative statement that you want the reader to remember about your study.

III. Problems to Avoid

Failure to be concise Your conclusion section should be concise and to the point. Conclusions that are too lengthy often have unnecessary information in them. The conclusion is not the place for details about your methodology or results. Although you should give a summary of what was learned from your research, this summary should be relatively brief, since the emphasis in the conclusion is on the implications, evaluations, insights, and other forms of analysis that you make. Strategies for writing concisely can be found here .

Failure to comment on larger, more significant issues In the introduction, your task was to move from the general [the field of study] to the specific [the research problem]. However, in the conclusion, your task is to move from a specific discussion [your research problem] back to a general discussion [i.e., how your research contributes new understanding or fills an important gap in the literature]. In short, the conclusion is where you should place your research within a larger context [visualize your paper as an hourglass--start with a broad introduction and review of the literature, move to the specific analysis and discussion, conclude with a broad summary of the study's implications and significance].

Failure to reveal problems and negative results Negative aspects of the research process should never be ignored. These are problems, deficiencies, or challenges encountered during your study should be summarized as a way of qualifying your overall conclusions. If you encountered negative or unintended results [i.e., findings that are validated outside the research context in which they were generated], you must report them in the results section and discuss their implications in the discussion section of your paper. In the conclusion, use your summary of the negative results as an opportunity to explain their possible significance and/or how they may form the basis for future research.

Failure to provide a clear summary of what was learned In order to be able to discuss how your research fits within your field of study [and possibly the world at large], you need to summarize briefly and succinctly how it contributes to new knowledge or a new understanding about the research problem. This element of your conclusion may be only a few sentences long.

Failure to match the objectives of your research Often research objectives in the social sciences change while the research is being carried out. This is not a problem unless you forget to go back and refine the original objectives in your introduction. As these changes emerge they must be documented so that they accurately reflect what you were trying to accomplish in your research [not what you thought you might accomplish when you began].

Resist the urge to apologize If you've immersed yourself in studying the research problem, you presumably should know a good deal about it [perhaps even more than your professor!]. Nevertheless, by the time you have finished writing, you may be having some doubts about what you have produced. Repress those doubts! Don't undermine your authority by saying something like, "This is just one approach to examining this problem; there may be other, much better approaches that...." The overall tone of your conclusion should convey confidence to the reader.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Concluding Paragraphs. College Writing Center at Meramec. St. Louis Community College; Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University; Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions. The Lab Report. University College Writing Centre. University of Toronto; Leibensperger, Summer. Draft Your Conclusion. Academic Center, the University of Houston-Victoria, 2003; Make Your Last Words Count. The Writer’s Handbook. Writing Center. University of Wisconsin Madison; Miquel, Fuster-Marquez and Carmen Gregori-Signes. “Chapter Six: ‘Last but Not Least:’ Writing the Conclusion of Your Paper.” In Writing an Applied Linguistics Thesis or Dissertation: A Guide to Presenting Empirical Research . John Bitchener, editor. (Basingstoke,UK: Palgrave Macmillan, 2010), pp. 93-105; Tips for Writing a Good Conclusion. Writing@CSU. Colorado State University; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Writing Conclusions. Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Writing: Considering Structure and Organization. Institute for Writing Rhetoric. Dartmouth College.

Writing Tip

Don't Belabor the Obvious!

Avoid phrases like "in conclusion...," "in summary...," or "in closing...." These phrases can be useful, even welcome, in oral presentations. But readers can see by the tell-tale section heading and number of pages remaining to read, when an essay is about to end. You'll irritate your readers if you belabor the obvious.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Another Writing Tip

New Insight, Not New Information!

Don't surprise the reader with new information in your conclusion that was never referenced anywhere else in the paper and, as such, the conclusion rarely has citations to sources. If you have new information to present, add it to the discussion or other appropriate section of the paper. Note that, although no actual new information is introduced, the conclusion, along with the discussion section, is where you offer your most "original" contributions in the paper; the conclusion is where you describe the value of your research, demonstrate that you understand the material that you’ve presented, and locate your findings within the larger context of scholarship on the topic, including describing how your research contributes new insights or valuable insight to that scholarship.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Conclusions. The Writing Center. University of North Carolina.

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case study the conclusion

How to Write the Perfect Conclusion to Your UX Case Study

If you nail your case study’s conclusion, you’re much likelier to get called to an interview, because employers tend to recall the last parts of a case study the most. Let’s see how you can craft the perfect ending to your UX case study.

So, you’ve written a great introductory hook to your UX case study, where you defined your problem statement, your approach to solving it and your role in the project. You then brought your reader through your design process and highlighted the decisions and challenges that led to your final result. One question remains: how do you end your UX case study with a bang? As it turns out, you need to include 3 things in your UX case study’s ending to make it truly satisfying: the final product, its impacts and your reflections.

What’s the Purpose of Your UX Case Study’s Conclusion?

To wrap your story up satisfactorily.

The conclusion of your UX case study serves as your story’s resolution. It’s where you tie up loose ends and close your story’s arc by answering the main question you asked in your introduction. When done right, your case study’s ending will create immense satisfaction and a lasting impression on a recruiter.

case study the conclusion

In the last part of your UX case study’s 5-part story arc, create a nice resolution to your story. The conclusion is where you bring everything together to leave your reader satisfied, if not wowed, with what you did and the outcome. Author / Copyright holder: Teo Yu Siang and the Interaction Design Foundation. Copyright terms and license: CC BY-NC-SA 3.0.

To Create a Great Last Impression

The lasting impression you create through your UX case study’s conclusion is absolutely vital. This is because of the serial-position effect , discovered by the German psychologist Hermann Ebbinghaus, where people tend to remember the first and last parts of a series best and forget the middle parts the most.

For instance, do you remember your most recent stay at a hotel? Chances are, you can recall how your stay ended when you checked out and how it began when you checked in—but nothing much of the middle. That’s the serial-position effect.

case study the conclusion

In 1913, Hermann Ebbinghaus discovered that we tend to remember only the beginnings and endings of things, and largely forget the middle parts. This means your UX case study’s introduction and conclusion are crucial parts! Author / copyright holder: Teo Yu Siang and the Interaction Design Foundation. Copyright terms and license: CC BY-NC-SA 3.0.

In particular, the serial-position effect is found to be strongest in the last items of a list. People tend to recall the last parts of an experience the most —that’s how vital your UX case study’s ending is! That isn’t to say you can afford to neglect any part of your case study’s middle part, though—it’s merely a scientific observation as to how recruiters will remember you. In other words, if you nail your case study’s conclusion, you’re much likelier to get called to an interview.

How Long Should Your UX Case Study’s Conclusion Be?

Your conclusion should ideally be as short as your introduction, or 4–5 sentences long . However, unlike in an introduction, you’ve got room for flexibility in your conclusion. That’s because while your introduction’s role is to quickly provide the needed information to move on to the main story, your conclusion has a different purpose—to make a great last impression. So, if you think a slightly longer conclusion can impress a recruiter more, you should go for it.

For instance, if you’ve got interesting lessons learnt or incredible results, you can afford to make your conclusion slightly longer, at around 3–4 paragraphs. Generally, the longer your case study’s middle portion is, the longer you can make your conclusion. But just like any other part of your case study, include only the essential and remove the rest. Every word counts!

3 Things You Should Include in Your UX Case Study’s Conclusion

A great UX case study’s ending contains these 3 things:

The final product;

Results and impact of the final product; and

Reflections and lessons learnt.

1. Show the Final Product

If you haven’t already showcased your final product in the middle part of your UX case study, now is the time to show it. Your final product will differ from project to project. For instance, a design thinking project will likely have a high-fidelity prototype as the final product. In a user research project, however, the final deliverable might be a set of user personas or a research report that contains recommendations.

If your final product is visual in nature—for example, an app—show it in a visual way. Screenshots, videos and interactive embedded prototypes are great ways to impress a recruiter. At the same time, practice restraint so that you don’t dump 100 photos of your entire project. Use only the most impactful ones.

If you’ve revamped an existing design, then this is a great time to showcase a before-and-after comparison. Include some screenshots of the problems in the old design in your introduction—and show and point out where you’ve improved it in your conclusion.

Even if your role is specialized and you therefore didn’t contribute directly to the final design of a product, you can still show the final product. This helps recruiters understand how your work shaped the final results. For example, if you specialize in visual design and have created an icon library, feel free to show how the icons are used throughout the product. If you do so, remember to make it clear what you worked on and what your colleagues created.

2. Demonstrate the Impacts of Your Project

Results are a must-have in your case study’s conclusion. Recruiters hire you to bring value to their organization, so they want to see the impact your work has generated.

Show results that are linked to the problem statement you introduced at the beginning of your case study. Since your problem statement should involve a business need, your results should also be business-oriented . For instance, show how your work has improved conversion rates or decreased drop-off rates. If you’ve created an app, show the app download or user rating metrics.

We encourage you to show numerical results, because they easily show your impact on a business. However, you can also show qualitative results—for instance, you can quote positive feedback and anecdotes from users and stakeholders .

case study the conclusion

Product designer Simon Pan’s UX case study is a great example of how to show the business results of your project. In his case study on his work for the ridesharing app Uber, Simon clearly shows how his work positively impacted the business. Author / copyright holder: Simon Pan. Copyright terms and license: Fair use.

3. Reflect on What You’ve Learnt

It’s vital that you reflect on your work in your conclusion. That’s how you create a sense of resolution and end in a satisfying way.

Furthermore, recruiters like to see designers who reflect on what they’ve learnt. According to Anett Illés from the UX design portfolio site UX Folio:

“UX recruiters and UX leads search for problem solvers motivated to explore and learn new things. So don’t hide your thirst for knowledge. On the contrary, highlight it!”

—Anett Illés, UX Folio

If you’re stuck at coming up with reflections, here are some questions you can ask yourself:

What is your main challenge in the project, and how have you handled it? For example, it could be the first time you’ve ever led a project. Or the project could’ve required you to step out of your comfort zone. Ideally, you should include a challenge that you have overcome, although sometimes a failure can make for an effective reflection, too.

What are some lessons you’ve learnt through the project? We are bound to make mistakes in our projects—and while we shouldn’t dwell on them in our UX case studies , we can turn them into learning points. Demonstrate how you’ve grown through your project.

Has the project changed your outlook as a designer? For instance, you could’ve learnt that a designer’s job is not only to delight users but also to bring value to the business.

What are your next steps for the project? Remember that design is an iterative process, so there’s no clear end point. If you could, how would you continue your work and take your project to the next level?

Download Our Template to Guide You

We’ve created a PDF guide to help you write your UX case study’s conclusion. Download your copy now:

3 Things to Include in Your UX Case Study’s Conclusion

An Example of a UX Case Study Conclusion

Let’s end with a sample conclusion we’ve created. This hypothetical UX case study is a design thinking project where we redesigned the home page of an ecommerce site. In this case study, we’ll assume that we’ve already introduced the final product in our middle portion.

We start with a long, first draft of our conclusion. We’ve included headings so you can clearly see its different components:

Results and impact: Compared with the previous version of the home page, our newly designed home page increased the conversion rate by 20%. Our admin team also reported a marked drop in the number of enquiries about how the platform works, which demonstrates an increase in ease of understanding. Main challenge and lesson learnt: This was the first time I led a project. Although I was nervous at the beginning, I soon learnt to trust my team-mates. I also learnt that active communication and short daily stand-up meetings were key to ensuring the project’s success. Next steps: This home page redesign validated our hypothesis that the most effective value proposition is one that is centered around a person’s core motivation . I’m looking forward to applying the same approach to other key pages of the platform.

Now that we’ve got all the main points, we can focus on shortening it to fit 4–5 sentences. Don’t skip this step, because it will make your conclusion drastically better!

Here’s our shortened and final conclusion:

Our redesigned home page had a 20% higher conversion rate. We also received fewer enquiries about how the platform works, which shows the new design is easier to understand. This was the first time I led a project. While I was nervous initially, I learnt to trust my team-mates and that daily stand-up meetings were key to the project’s success. This project validated the value of using copy that is centered around a person’s core motivation, and I look forward to applying the same approach to the rest of the site.

If you’ve revamped an existing design, you should also point out the specific areas you’ve improved in the design.

The Take Away

A well-written conclusion to a UX case study ensures that a recruiter leaves with a great last impression. This is extremely valuable because we tend to remember the last parts of an experience best, due to what’s called the serial-position effect.

Your conclusion should be 4–5 sentences long, although a longer middle portion or more elaborate reflections and results can justify a lengthier conclusion. To create a satisfying end to your project’s story and deliver a great last impression, you should include the following in your UX case study’s conclusion:

The final product (if you’ve not already shown it in your case study’s middle portion);

Business-oriented results and impacts of your project; and

Reflections on your work.

References and Where to Learn More

Our UX case study writing guides take inspiration from Gustav Freytag’s 5-part story structure, also called Freytag’s Pyramid. The pyramid was first written in Freytag’s 1863 book Die Technik des Dramas , or “Technique of the Drama”.

Hermann Ebbinghaus first published about the serial-position effect in 1913 in his paper titled “On memory: A contribution to experimental psychology” .

You can check out Simon Pan’s UX design portfolio for inspiration:

Your use of English can make or break your UX case study. Check out our guide, which contains 8 tips to write effectively

Anett Illés writes about how to follow UX recruiters’ logic in your UX case study in her article in UX Folio

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One of the most common questions we receive at the Writing Center is “what am I supposed to do in my conclusion?” This is a difficult question to answer because there’s no one right answer to what belongs in a conclusion. How you conclude your paper will depend on where you started—and where you traveled. It will also depend on the conventions and expectations of the discipline in which you are writing. For example, while the conclusion to a STEM paper could focus on questions for further study, the conclusion of a literature paper could include a quotation from your central text that can now be understood differently in light of what has been discussed in the paper. You should consult your instructor about expectations for conclusions in a particular discipline.

With that in mind, here are some general guidelines you might find helpful to use as you think about your conclusion.  

Begin with the “what”  

In a short paper—even a research paper—you don’t need to provide an exhaustive summary as part of your conclusion. But you do need to make some kind of transition between your final body paragraph and your concluding paragraph. This may come in the form of a few sentences of summary. Or it may come in the form of a sentence that brings your readers back to your thesis or main idea and reminds your readers where you began and how far you have traveled.

So, for example, in a paper about the relationship between ADHD and rejection sensitivity, Vanessa Roser begins by introducing readers to the fact that researchers have studied the relationship between the two conditions and then provides her explanation of that relationship. Here’s her thesis: “While socialization may indeed be an important factor in RS, I argue that individuals with ADHD may also possess a neurological predisposition to RS that is exacerbated by the differing executive and emotional regulation characteristic of ADHD.”

In her final paragraph, Roser reminds us of where she started by echoing her thesis: “This literature demonstrates that, as with many other conditions, ADHD and RS share a delicately intertwined pattern of neurological similarities that is rooted in the innate biology of an individual’s mind, a connection that cannot be explained in full by the behavioral mediation hypothesis.”  

Highlight the “so what”  

At the beginning of your paper, you explain to your readers what’s at stake—why they should care about the argument you’re making. In your conclusion, you can bring readers back to those stakes by reminding them why your argument is important in the first place. You can also draft a few sentences that put those stakes into a new or broader context.

In the conclusion to her paper about ADHD and RS, Roser echoes the stakes she established in her introduction—that research into connections between ADHD and RS has led to contradictory results, raising questions about the “behavioral mediation hypothesis.”

She writes, “as with many other conditions, ADHD and RS share a delicately intertwined pattern of neurological similarities that is rooted in the innate biology of an individual’s mind, a connection that cannot be explained in full by the behavioral mediation hypothesis.”  

Leave your readers with the “now what”  

After the “what” and the “so what,” you should leave your reader with some final thoughts. If you have written a strong introduction, your readers will know why you have been arguing what you have been arguing—and why they should care. And if you’ve made a good case for your thesis, then your readers should be in a position to see things in a new way, understand new questions, or be ready for something that they weren’t ready for before they read your paper.

In her conclusion, Roser offers two “now what” statements. First, she explains that it is important to recognize that the flawed behavioral mediation hypothesis “seems to place a degree of fault on the individual. It implies that individuals with ADHD must have elicited such frequent or intense rejection by virtue of their inadequate social skills, erasing the possibility that they may simply possess a natural sensitivity to emotion.” She then highlights the broader implications for treatment of people with ADHD, noting that recognizing the actual connection between rejection sensitivity and ADHD “has profound implications for understanding how individuals with ADHD might best be treated in educational settings, by counselors, family, peers, or even society as a whole.”

To find your own “now what” for your essay’s conclusion, try asking yourself these questions:

  • What can my readers now understand, see in a new light, or grapple with that they would not have understood in the same way before reading my paper? Are we a step closer to understanding a larger phenomenon or to understanding why what was at stake is so important?  
  • What questions can I now raise that would not have made sense at the beginning of my paper? Questions for further research? Other ways that this topic could be approached?  
  • Are there other applications for my research? Could my questions be asked about different data in a different context? Could I use my methods to answer a different question?  
  • What action should be taken in light of this argument? What action do I predict will be taken or could lead to a solution?  
  • What larger context might my argument be a part of?  

What to avoid in your conclusion  

  • a complete restatement of all that you have said in your paper.  
  • a substantial counterargument that you do not have space to refute; you should introduce counterarguments before your conclusion.  
  • an apology for what you have not said. If you need to explain the scope of your paper, you should do this sooner—but don’t apologize for what you have not discussed in your paper.  
  • fake transitions like “in conclusion” that are followed by sentences that aren’t actually conclusions. (“In conclusion, I have now demonstrated that my thesis is correct.”)
  • picture_as_pdf Conclusions

The Writing Center • University of North Carolina at Chapel Hill

Conclusions

What this handout is about.

This handout will explain the functions of conclusions, offer strategies for writing effective ones, help you evaluate conclusions you’ve drafted, and suggest approaches to avoid.

About conclusions

Introductions and conclusions can be difficult to write, but they’re worth investing time in. They can have a significant influence on a reader’s experience of your paper.

Just as your introduction acts as a bridge that transports your readers from their own lives into the “place” of your analysis, your conclusion can provide a bridge to help your readers make the transition back to their daily lives. Such a conclusion will help them see why all your analysis and information should matter to them after they put the paper down.

Your conclusion is your chance to have the last word on the subject. The conclusion allows you to have the final say on the issues you have raised in your paper, to synthesize your thoughts, to demonstrate the importance of your ideas, and to propel your reader to a new view of the subject. It is also your opportunity to make a good final impression and to end on a positive note.

Your conclusion can go beyond the confines of the assignment. The conclusion pushes beyond the boundaries of the prompt and allows you to consider broader issues, make new connections, and elaborate on the significance of your findings.

Your conclusion should make your readers glad they read your paper. Your conclusion gives your reader something to take away that will help them see things differently or appreciate your topic in personally relevant ways. It can suggest broader implications that will not only interest your reader, but also enrich your reader’s life in some way. It is your gift to the reader.

Strategies for writing an effective conclusion

One or more of the following strategies may help you write an effective conclusion:

  • Play the “So What” Game. If you’re stuck and feel like your conclusion isn’t saying anything new or interesting, ask a friend to read it with you. Whenever you make a statement from your conclusion, ask the friend to say, “So what?” or “Why should anybody care?” Then ponder that question and answer it. Here’s how it might go: You: Basically, I’m just saying that education was important to Douglass. Friend: So what? You: Well, it was important because it was a key to him feeling like a free and equal citizen. Friend: Why should anybody care? You: That’s important because plantation owners tried to keep slaves from being educated so that they could maintain control. When Douglass obtained an education, he undermined that control personally. You can also use this strategy on your own, asking yourself “So What?” as you develop your ideas or your draft.
  • Return to the theme or themes in the introduction. This strategy brings the reader full circle. For example, if you begin by describing a scenario, you can end with the same scenario as proof that your essay is helpful in creating a new understanding. You may also refer to the introductory paragraph by using key words or parallel concepts and images that you also used in the introduction.
  • Synthesize, don’t summarize. Include a brief summary of the paper’s main points, but don’t simply repeat things that were in your paper. Instead, show your reader how the points you made and the support and examples you used fit together. Pull it all together.
  • Include a provocative insight or quotation from the research or reading you did for your paper.
  • Propose a course of action, a solution to an issue, or questions for further study. This can redirect your reader’s thought process and help her to apply your info and ideas to her own life or to see the broader implications.
  • Point to broader implications. For example, if your paper examines the Greensboro sit-ins or another event in the Civil Rights Movement, you could point out its impact on the Civil Rights Movement as a whole. A paper about the style of writer Virginia Woolf could point to her influence on other writers or on later feminists.

Strategies to avoid

  • Beginning with an unnecessary, overused phrase such as “in conclusion,” “in summary,” or “in closing.” Although these phrases can work in speeches, they come across as wooden and trite in writing.
  • Stating the thesis for the very first time in the conclusion.
  • Introducing a new idea or subtopic in your conclusion.
  • Ending with a rephrased thesis statement without any substantive changes.
  • Making sentimental, emotional appeals that are out of character with the rest of an analytical paper.
  • Including evidence (quotations, statistics, etc.) that should be in the body of the paper.

Four kinds of ineffective conclusions

  • The “That’s My Story and I’m Sticking to It” Conclusion. This conclusion just restates the thesis and is usually painfully short. It does not push the ideas forward. People write this kind of conclusion when they can’t think of anything else to say. Example: In conclusion, Frederick Douglass was, as we have seen, a pioneer in American education, proving that education was a major force for social change with regard to slavery.
  • The “Sherlock Holmes” Conclusion. Sometimes writers will state the thesis for the very first time in the conclusion. You might be tempted to use this strategy if you don’t want to give everything away too early in your paper. You may think it would be more dramatic to keep the reader in the dark until the end and then “wow” him with your main idea, as in a Sherlock Holmes mystery. The reader, however, does not expect a mystery, but an analytical discussion of your topic in an academic style, with the main argument (thesis) stated up front. Example: (After a paper that lists numerous incidents from the book but never says what these incidents reveal about Douglass and his views on education): So, as the evidence above demonstrates, Douglass saw education as a way to undermine the slaveholders’ power and also an important step toward freedom.
  • The “America the Beautiful”/”I Am Woman”/”We Shall Overcome” Conclusion. This kind of conclusion usually draws on emotion to make its appeal, but while this emotion and even sentimentality may be very heartfelt, it is usually out of character with the rest of an analytical paper. A more sophisticated commentary, rather than emotional praise, would be a more fitting tribute to the topic. Example: Because of the efforts of fine Americans like Frederick Douglass, countless others have seen the shining beacon of light that is education. His example was a torch that lit the way for others. Frederick Douglass was truly an American hero.
  • The “Grab Bag” Conclusion. This kind of conclusion includes extra information that the writer found or thought of but couldn’t integrate into the main paper. You may find it hard to leave out details that you discovered after hours of research and thought, but adding random facts and bits of evidence at the end of an otherwise-well-organized essay can just create confusion. Example: In addition to being an educational pioneer, Frederick Douglass provides an interesting case study for masculinity in the American South. He also offers historians an interesting glimpse into slave resistance when he confronts Covey, the overseer. His relationships with female relatives reveal the importance of family in the slave community.

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Douglass, Frederick. 1995. Narrative of the Life of Frederick Douglass, an American Slave, Written by Himself. New York: Dover.

Hamilton College. n.d. “Conclusions.” Writing Center. Accessed June 14, 2019. https://www.hamilton.edu//academics/centers/writing/writing-resources/conclusions .

Holewa, Randa. 2004. “Strategies for Writing a Conclusion.” LEO: Literacy Education Online. Last updated February 19, 2004. https://leo.stcloudstate.edu/acadwrite/conclude.html.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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All You Wanted to Know About How to Write a Case Study

case study the conclusion

What do you study in your college? If you are a psychology, sociology, or anthropology student, we bet you might be familiar with what a case study is. This research method is used to study a certain person, group, or situation. In this guide from our dissertation writing service , you will learn how to write a case study professionally, from researching to citing sources properly. Also, we will explore different types of case studies and show you examples — so that you won’t have any other questions left.

What Is a Case Study?

A case study is a subcategory of research design which investigates problems and offers solutions. Case studies can range from academic research studies to corporate promotional tools trying to sell an idea—their scope is quite vast.

What Is the Difference Between a Research Paper and a Case Study?

While research papers turn the reader’s attention to a certain problem, case studies go even further. Case study guidelines require students to pay attention to details, examining issues closely and in-depth using different research methods. For example, case studies may be used to examine court cases if you study Law, or a patient's health history if you study Medicine. Case studies are also used in Marketing, which are thorough, empirically supported analysis of a good or service's performance. Well-designed case studies can be valuable for prospective customers as they can identify and solve the potential customers pain point.

Case studies involve a lot of storytelling – they usually examine particular cases for a person or a group of people. This method of research is very helpful, as it is very practical and can give a lot of hands-on information. Most commonly, the length of the case study is about 500-900 words, which is much less than the length of an average research paper.

The structure of a case study is very similar to storytelling. It has a protagonist or main character, which in your case is actually a problem you are trying to solve. You can use the system of 3 Acts to make it a compelling story. It should have an introduction, rising action, a climax where transformation occurs, falling action, and a solution.

Here is a rough formula for you to use in your case study:

Problem (Act I): > Solution (Act II) > Result (Act III) > Conclusion.

Types of Case Studies

The purpose of a case study is to provide detailed reports on an event, an institution, a place, future customers, or pretty much anything. There are a few common types of case study, but the type depends on the topic. The following are the most common domains where case studies are needed:

Types of Case Studies

  • Historical case studies are great to learn from. Historical events have a multitude of source info offering different perspectives. There are always modern parallels where these perspectives can be applied, compared, and thoroughly analyzed.
  • Problem-oriented case studies are usually used for solving problems. These are often assigned as theoretical situations where you need to immerse yourself in the situation to examine it. Imagine you’re working for a startup and you’ve just noticed a significant flaw in your product’s design. Before taking it to the senior manager, you want to do a comprehensive study on the issue and provide solutions. On a greater scale, problem-oriented case studies are a vital part of relevant socio-economic discussions.
  • Cumulative case studies collect information and offer comparisons. In business, case studies are often used to tell people about the value of a product.
  • Critical case studies explore the causes and effects of a certain case.
  • Illustrative case studies describe certain events, investigating outcomes and lessons learned.

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Case Study Format

The case study format is typically made up of eight parts:

  • Executive Summary. Explain what you will examine in the case study. Write an overview of the field you’re researching. Make a thesis statement and sum up the results of your observation in a maximum of 2 sentences.
  • Background. Provide background information and the most relevant facts. Isolate the issues.
  • Case Evaluation. Isolate the sections of the study you want to focus on. In it, explain why something is working or is not working.
  • Proposed Solutions. Offer realistic ways to solve what isn’t working or how to improve its current condition. Explain why these solutions work by offering testable evidence.
  • Conclusion. Summarize the main points from the case evaluations and proposed solutions. 6. Recommendations. Talk about the strategy that you should choose. Explain why this choice is the most appropriate.
  • Implementation. Explain how to put the specific strategies into action.
  • References. Provide all the citations.

How to Write a Case Study

Let's discover how to write a case study.

How to Write a Case Study

Setting Up the Research

When writing a case study, remember that research should always come first. Reading many different sources and analyzing other points of view will help you come up with more creative solutions. You can also conduct an actual interview to thoroughly investigate the customer story that you'll need for your case study. Including all of the necessary research, writing a case study may take some time. The research process involves doing the following:

  • Define your objective. Explain the reason why you’re presenting your subject. Figure out where you will feature your case study; whether it is written, on video, shown as an infographic, streamed as a podcast, etc.
  • Determine who will be the right candidate for your case study. Get permission, quotes, and other features that will make your case study effective. Get in touch with your candidate to see if they approve of being part of your work. Study that candidate’s situation and note down what caused it.
  • Identify which various consequences could result from the situation. Follow these guidelines on how to start a case study: surf the net to find some general information you might find useful.
  • Make a list of credible sources and examine them. Seek out important facts and highlight problems. Always write down your ideas and make sure to brainstorm.
  • Focus on several key issues – why they exist, and how they impact your research subject. Think of several unique solutions. Draw from class discussions, readings, and personal experience. When writing a case study, focus on the best solution and explore it in depth. After having all your research in place, writing a case study will be easy. You may first want to check the rubric and criteria of your assignment for the correct case study structure.

Read Also: 'CREDIBLE SOURCES: WHAT ARE THEY?'

Although your instructor might be looking at slightly different criteria, every case study rubric essentially has the same standards. Your professor will want you to exhibit 8 different outcomes:

  • Correctly identify the concepts, theories, and practices in the discipline.
  • Identify the relevant theories and principles associated with the particular study.
  • Evaluate legal and ethical principles and apply them to your decision-making.
  • Recognize the global importance and contribution of your case.
  • Construct a coherent summary and explanation of the study.
  • Demonstrate analytical and critical-thinking skills.
  • Explain the interrelationships between the environment and nature.
  • Integrate theory and practice of the discipline within the analysis.

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Case Study Outline

Let's look at the structure of an outline based on the issue of the alcoholic addiction of 30 people.

Introduction

  • Statement of the issue: Alcoholism is a disease rather than a weakness of character.
  • Presentation of the problem: Alcoholism is affecting more than 14 million people in the USA, which makes it the third most common mental illness there.
  • Explanation of the terms: In the past, alcoholism was commonly referred to as alcohol dependence or alcohol addiction. Alcoholism is now the more severe stage of this addiction in the disorder spectrum.
  • Hypotheses: Drinking in excess can lead to the use of other drugs.
  • Importance of your story: How the information you present can help people with their addictions.
  • Background of the story: Include an explanation of why you chose this topic.
  • Presentation of analysis and data: Describe the criteria for choosing 30 candidates, the structure of the interview, and the outcomes.
  • Strong argument 1: ex. X% of candidates dealing with anxiety and depression...
  • Strong argument 2: ex. X amount of people started drinking by their mid-teens.
  • Strong argument 3: ex. X% of respondents’ parents had issues with alcohol.
  • Concluding statement: I have researched if alcoholism is a disease and found out that…
  • Recommendations: Ways and actions for preventing alcohol use.

Writing a Case Study Draft

After you’ve done your case study research and written the outline, it’s time to focus on the draft. In a draft, you have to develop and write your case study by using: the data which you collected throughout the research, interviews, and the analysis processes that were undertaken. Follow these rules for the draft:

How to Write a Case Study

  • Your draft should contain at least 4 sections: an introduction; a body where you should include background information, an explanation of why you decided to do this case study, and a presentation of your main findings; a conclusion where you present data; and references.
  • In the introduction, you should set the pace very clearly. You can even raise a question or quote someone you interviewed in the research phase. It must provide adequate background information on the topic. The background may include analyses of previous studies on your topic. Include the aim of your case here as well. Think of it as a thesis statement. The aim must describe the purpose of your work—presenting the issues that you want to tackle. Include background information, such as photos or videos you used when doing the research.
  • Describe your unique research process, whether it was through interviews, observations, academic journals, etc. The next point includes providing the results of your research. Tell the audience what you found out. Why is this important, and what could be learned from it? Discuss the real implications of the problem and its significance in the world.
  • Include quotes and data (such as findings, percentages, and awards). This will add a personal touch and better credibility to the case you present. Explain what results you find during your interviews in regards to the problem and how it developed. Also, write about solutions which have already been proposed by other people who have already written about this case.
  • At the end of your case study, you should offer possible solutions, but don’t worry about solving them yourself.

Use Data to Illustrate Key Points in Your Case Study

Even though your case study is a story, it should be based on evidence. Use as much data as possible to illustrate your point. Without the right data, your case study may appear weak and the readers may not be able to relate to your issue as much as they should. Let's see the examples from essay writing service :

‍ With data: Alcoholism is affecting more than 14 million people in the USA, which makes it the third most common mental illness there. Without data: A lot of people suffer from alcoholism in the United States.

Try to include as many credible sources as possible. You may have terms or sources that could be hard for other cultures to understand. If this is the case, you should include them in the appendix or Notes for the Instructor or Professor.

Finalizing the Draft: Checklist

After you finish drafting your case study, polish it up by answering these ‘ask yourself’ questions and think about how to end your case study:

  • Check that you follow the correct case study format, also in regards to text formatting.
  • Check that your work is consistent with its referencing and citation style.
  • Micro-editing — check for grammar and spelling issues.
  • Macro-editing — does ‘the big picture’ come across to the reader? Is there enough raw data, such as real-life examples or personal experiences? Have you made your data collection process completely transparent? Does your analysis provide a clear conclusion, allowing for further research and practice?

Problems to avoid:

  • Overgeneralization – Do not go into further research that deviates from the main problem.
  • Failure to Document Limitations – Just as you have to clearly state the limitations of a general research study, you must describe the specific limitations inherent in the subject of analysis.
  • Failure to Extrapolate All Possible Implications – Just as you don't want to over-generalize from your case study findings, you also have to be thorough in the consideration of all possible outcomes or recommendations derived from your findings.

How to Create a Title Page and Cite a Case Study

Let's see how to create an awesome title page.

Your title page depends on the prescribed citation format. The title page should include:

  • A title that attracts some attention and describes your study
  • The title should have the words “case study” in it
  • The title should range between 5-9 words in length
  • Your name and contact information
  • Your finished paper should be only 500 to 1,500 words in length. With this type of assignment, write effectively and avoid fluff.

Here is a template for the APA and MLA format title page:

There are some cases when you need to cite someone else's study in your own one – therefore, you need to master how to cite a case study. A case study is like a research paper when it comes to citations. You can cite it like you cite a book, depending on what style you need.

Citation Example in MLA ‍ Hill, Linda, Tarun Khanna, and Emily A. Stecker. HCL Technologies. Boston: Harvard Business Publishing, 2008. Print.
Citation Example in APA ‍ Hill, L., Khanna, T., & Stecker, E. A. (2008). HCL Technologies. Boston: Harvard Business Publishing.
Citation Example in Chicago Hill, Linda, Tarun Khanna, and Emily A. Stecker. HCL Technologies.

Case Study Examples

To give you an idea of a professional case study example, we gathered and linked some below.

Eastman Kodak Case Study

Case Study Example: Audi Trains Mexican Autoworkers in Germany

To conclude, a case study is one of the best methods of getting an overview of what happened to a person, a group, or a situation in practice. It allows you to have an in-depth glance at the real-life problems that businesses, healthcare industry, criminal justice, etc. may face. This insight helps us look at such situations in a different light. This is because we see scenarios that we otherwise would not, without necessarily being there. If you need custom essays , try our research paper writing services .

Get Help Form Qualified Writers

Crafting a case study is not easy. You might want to write one of high quality, but you don’t have the time or expertise. If you’re having trouble with your case study, help with essay request - we'll help. EssayPro writers have read and written countless case studies and are experts in endless disciplines. Request essay writing, editing, or proofreading assistance from our custom case study writing service , and all of your worries will be gone.

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  • How to Write Discussions and Conclusions

How to Write Discussions and Conclusions

The discussion section contains the results and outcomes of a study. An effective discussion informs readers what can be learned from your experiment and provides context for the results.

What makes an effective discussion?

When you’re ready to write your discussion, you’ve already introduced the purpose of your study and provided an in-depth description of the methodology. The discussion informs readers about the larger implications of your study based on the results. Highlighting these implications while not overstating the findings can be challenging, especially when you’re submitting to a journal that selects articles based on novelty or potential impact. Regardless of what journal you are submitting to, the discussion section always serves the same purpose: concluding what your study results actually mean.

A successful discussion section puts your findings in context. It should include:

  • the results of your research,
  • a discussion of related research, and
  • a comparison between your results and initial hypothesis.

Tip: Not all journals share the same naming conventions.

You can apply the advice in this article to the conclusion, results or discussion sections of your manuscript.

Our Early Career Researcher community tells us that the conclusion is often considered the most difficult aspect of a manuscript to write. To help, this guide provides questions to ask yourself, a basic structure to model your discussion off of and examples from published manuscripts. 

case study the conclusion

Questions to ask yourself:

  • Was my hypothesis correct?
  • If my hypothesis is partially correct or entirely different, what can be learned from the results? 
  • How do the conclusions reshape or add onto the existing knowledge in the field? What does previous research say about the topic? 
  • Why are the results important or relevant to your audience? Do they add further evidence to a scientific consensus or disprove prior studies? 
  • How can future research build on these observations? What are the key experiments that must be done? 
  • What is the “take-home” message you want your reader to leave with?

How to structure a discussion

Trying to fit a complete discussion into a single paragraph can add unnecessary stress to the writing process. If possible, you’ll want to give yourself two or three paragraphs to give the reader a comprehensive understanding of your study as a whole. Here’s one way to structure an effective discussion:

case study the conclusion

Writing Tips

While the above sections can help you brainstorm and structure your discussion, there are many common mistakes that writers revert to when having difficulties with their paper. Writing a discussion can be a delicate balance between summarizing your results, providing proper context for your research and avoiding introducing new information. Remember that your paper should be both confident and honest about the results! 

What to do

  • Read the journal’s guidelines on the discussion and conclusion sections. If possible, learn about the guidelines before writing the discussion to ensure you’re writing to meet their expectations. 
  • Begin with a clear statement of the principal findings. This will reinforce the main take-away for the reader and set up the rest of the discussion. 
  • Explain why the outcomes of your study are important to the reader. Discuss the implications of your findings realistically based on previous literature, highlighting both the strengths and limitations of the research. 
  • State whether the results prove or disprove your hypothesis. If your hypothesis was disproved, what might be the reasons? 
  • Introduce new or expanded ways to think about the research question. Indicate what next steps can be taken to further pursue any unresolved questions. 
  • If dealing with a contemporary or ongoing problem, such as climate change, discuss possible consequences if the problem is avoided. 
  • Be concise. Adding unnecessary detail can distract from the main findings. 

What not to do

Don’t

  • Rewrite your abstract. Statements with “we investigated” or “we studied” generally do not belong in the discussion. 
  • Include new arguments or evidence not previously discussed. Necessary information and evidence should be introduced in the main body of the paper. 
  • Apologize. Even if your research contains significant limitations, don’t undermine your authority by including statements that doubt your methodology or execution. 
  • Shy away from speaking on limitations or negative results. Including limitations and negative results will give readers a complete understanding of the presented research. Potential limitations include sources of potential bias, threats to internal or external validity, barriers to implementing an intervention and other issues inherent to the study design. 
  • Overstate the importance of your findings. Making grand statements about how a study will fully resolve large questions can lead readers to doubt the success of the research. 

Snippets of Effective Discussions:

Consumer-based actions to reduce plastic pollution in rivers: A multi-criteria decision analysis approach

Identifying reliable indicators of fitness in polar bears

  • How to Write a Great Title
  • How to Write an Abstract
  • How to Write Your Methods
  • How to Report Statistics
  • How to Edit Your Work

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How to Write a Conclusion for Research Papers (with Examples)

How to Write a Conclusion for Research Papers (with Examples)

The conclusion of a research paper is a crucial section that plays a significant role in the overall impact and effectiveness of your research paper. However, this is also the section that typically receives less attention compared to the introduction and the body of the paper. The conclusion serves to provide a concise summary of the key findings, their significance, their implications, and a sense of closure to the study. Discussing how can the findings be applied in real-world scenarios or inform policy, practice, or decision-making is especially valuable to practitioners and policymakers. The research paper conclusion also provides researchers with clear insights and valuable information for their own work, which they can then build on and contribute to the advancement of knowledge in the field.

The research paper conclusion should explain the significance of your findings within the broader context of your field. It restates how your results contribute to the existing body of knowledge and whether they confirm or challenge existing theories or hypotheses. Also, by identifying unanswered questions or areas requiring further investigation, your awareness of the broader research landscape can be demonstrated.

Remember to tailor the research paper conclusion to the specific needs and interests of your intended audience, which may include researchers, practitioners, policymakers, or a combination of these.

Table of Contents

What is a conclusion in a research paper, summarizing conclusion, editorial conclusion, externalizing conclusion, importance of a good research paper conclusion, how to write a conclusion for your research paper, research paper conclusion examples, frequently asked questions.

A conclusion in a research paper is the final section where you summarize and wrap up your research, presenting the key findings and insights derived from your study. The research paper conclusion is not the place to introduce new information or data that was not discussed in the main body of the paper. When working on how to conclude a research paper, remember to stick to summarizing and interpreting existing content. The research paper conclusion serves the following purposes: 1

  • Warn readers of the possible consequences of not attending to the problem.
  • Recommend specific course(s) of action.
  • Restate key ideas to drive home the ultimate point of your research paper.
  • Provide a “take-home” message that you want the readers to remember about your study.

case study the conclusion

Types of conclusions for research papers

In research papers, the conclusion provides closure to the reader. The type of research paper conclusion you choose depends on the nature of your study, your goals, and your target audience. I provide you with three common types of conclusions:

A summarizing conclusion is the most common type of conclusion in research papers. It involves summarizing the main points, reiterating the research question, and restating the significance of the findings. This common type of research paper conclusion is used across different disciplines.

An editorial conclusion is less common but can be used in research papers that are focused on proposing or advocating for a particular viewpoint or policy. It involves presenting a strong editorial or opinion based on the research findings and offering recommendations or calls to action.

An externalizing conclusion is a type of conclusion that extends the research beyond the scope of the paper by suggesting potential future research directions or discussing the broader implications of the findings. This type of conclusion is often used in more theoretical or exploratory research papers.

The conclusion in a research paper serves several important purposes:

  • Offers Implications and Recommendations : Your research paper conclusion is an excellent place to discuss the broader implications of your research and suggest potential areas for further study. It’s also an opportunity to offer practical recommendations based on your findings.
  • Provides Closure : A good research paper conclusion provides a sense of closure to your paper. It should leave the reader with a feeling that they have reached the end of a well-structured and thought-provoking research project.
  • Leaves a Lasting Impression : Writing a well-crafted research paper conclusion leaves a lasting impression on your readers. It’s your final opportunity to leave them with a new idea, a call to action, or a memorable quote.

case study the conclusion

Writing a strong conclusion for your research paper is essential to leave a lasting impression on your readers. Here’s a step-by-step process to help you create and know what to put in the conclusion of a research paper: 2

  • Research Statement : Begin your research paper conclusion by restating your research statement. This reminds the reader of the main point you’ve been trying to prove throughout your paper. Keep it concise and clear.
  • Key Points : Summarize the main arguments and key points you’ve made in your paper. Avoid introducing new information in the research paper conclusion. Instead, provide a concise overview of what you’ve discussed in the body of your paper.
  • Address the Research Questions : If your research paper is based on specific research questions or hypotheses, briefly address whether you’ve answered them or achieved your research goals. Discuss the significance of your findings in this context.
  • Significance : Highlight the importance of your research and its relevance in the broader context. Explain why your findings matter and how they contribute to the existing knowledge in your field.
  • Implications : Explore the practical or theoretical implications of your research. How might your findings impact future research, policy, or real-world applications? Consider the “so what?” question.
  • Future Research : Offer suggestions for future research in your area. What questions or aspects remain unanswered or warrant further investigation? This shows that your work opens the door for future exploration.
  • Closing Thought : Conclude your research paper conclusion with a thought-provoking or memorable statement. This can leave a lasting impression on your readers and wrap up your paper effectively. Avoid introducing new information or arguments here.
  • Proofread and Revise : Carefully proofread your conclusion for grammar, spelling, and clarity. Ensure that your ideas flow smoothly and that your conclusion is coherent and well-structured.

Remember that a well-crafted research paper conclusion is a reflection of the strength of your research and your ability to communicate its significance effectively. It should leave a lasting impression on your readers and tie together all the threads of your paper. Now you know how to start the conclusion of a research paper and what elements to include to make it impactful, let’s look at a research paper conclusion sample.

case study the conclusion

The research paper conclusion is a crucial part of your paper as it provides the final opportunity to leave a strong impression on your readers. In the research paper conclusion, summarize the main points of your research paper by restating your research statement, highlighting the most important findings, addressing the research questions or objectives, explaining the broader context of the study, discussing the significance of your findings, providing recommendations if applicable, and emphasizing the takeaway message. The main purpose of the conclusion is to remind the reader of the main point or argument of your paper and to provide a clear and concise summary of the key findings and their implications. All these elements should feature on your list of what to put in the conclusion of a research paper to create a strong final statement for your work.

A strong conclusion is a critical component of a research paper, as it provides an opportunity to wrap up your arguments, reiterate your main points, and leave a lasting impression on your readers. Here are the key elements of a strong research paper conclusion: 1. Conciseness : A research paper conclusion should be concise and to the point. It should not introduce new information or ideas that were not discussed in the body of the paper. 2. Summarization : The research paper conclusion should be comprehensive enough to give the reader a clear understanding of the research’s main contributions. 3 . Relevance : Ensure that the information included in the research paper conclusion is directly relevant to the research paper’s main topic and objectives; avoid unnecessary details. 4 . Connection to the Introduction : A well-structured research paper conclusion often revisits the key points made in the introduction and shows how the research has addressed the initial questions or objectives. 5. Emphasis : Highlight the significance and implications of your research. Why is your study important? What are the broader implications or applications of your findings? 6 . Call to Action : Include a call to action or a recommendation for future research or action based on your findings.

The length of a research paper conclusion can vary depending on several factors, including the overall length of the paper, the complexity of the research, and the specific journal requirements. While there is no strict rule for the length of a conclusion, but it’s generally advisable to keep it relatively short. A typical research paper conclusion might be around 5-10% of the paper’s total length. For example, if your paper is 10 pages long, the conclusion might be roughly half a page to one page in length.

In general, you do not need to include citations in the research paper conclusion. Citations are typically reserved for the body of the paper to support your arguments and provide evidence for your claims. However, there may be some exceptions to this rule: 1. If you are drawing a direct quote or paraphrasing a specific source in your research paper conclusion, you should include a citation to give proper credit to the original author. 2. If your conclusion refers to or discusses specific research, data, or sources that are crucial to the overall argument, citations can be included to reinforce your conclusion’s validity.

The conclusion of a research paper serves several important purposes: 1. Summarize the Key Points 2. Reinforce the Main Argument 3. Provide Closure 4. Offer Insights or Implications 5. Engage the Reader. 6. Reflect on Limitations

Remember that the primary purpose of the research paper conclusion is to leave a lasting impression on the reader, reinforcing the key points and providing closure to your research. It’s often the last part of the paper that the reader will see, so it should be strong and well-crafted.

  • Makar, G., Foltz, C., Lendner, M., & Vaccaro, A. R. (2018). How to write effective discussion and conclusion sections. Clinical spine surgery, 31(8), 345-346.
  • Bunton, D. (2005). The structure of PhD conclusion chapters.  Journal of English for academic purposes ,  4 (3), 207-224.

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Writing the parts of scientific reports

22 Writing the conclusion & recommendations

There are probably some overlaps between the Conclusion and the Discussion section. Nevertheless, this section gives you the opportunity to highlight the most important points in your report, and is sometimes the only section read. Think about what your research/ study has achieved, and the most important findings and ideas you want the reader to know. As all studies have limitations also think about what you were not able to cover (this shows that you are able to evaluate your own work objectively).

Possible structure of this section:

case study the conclusion

Use present perfect to sum up/ evaluate:

This study has explored/ has attempted …

Use past tense to state what your aim was and to refer to actions you carried out:

  • This study was intended to analyse …
  • The aim of this study was to …

Use present tense to evaluate your study and to state the generalizations and implications that you draw from your findings.

  • The results add to the knowledge of …
  • These findings s uggest that …

You can either use present tense or past tense to summarize your results.

  • The findings reveal …
  • It was found that …

Achievements of this study (positive)

  • This study provides evidence that …
  • This work has contributed to a number of key issues in the field such as …

Limitations of the study (negative)

  • Several limitations should be noted. First …

Combine positive and negative remarks to give a balanced assessment:

  • Although this research is somewhat limited in scope, its findings can provide a basis for future studies.
  • Despite the limitations, findings from the present study can help us understand …

Use more cautious language (modal verbs may, can, could)

  • There are a number of possible extensions of this research …
  • The findings suggest the possibility for future research on …
  • These results may be important for future studies on …
  • Examining a wider context could/ would lead …

Or indicate that future research is needed

  • There is still a need for future research to determine …
  • Further studies should be undertaken to discover…
  • It would be worthwhile to investigate …

case study the conclusion

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Research Method

Home » Case Study – Methods, Examples and Guide

Case Study – Methods, Examples and Guide

Table of Contents

Case Study Research

A case study is a research method that involves an in-depth examination and analysis of a particular phenomenon or case, such as an individual, organization, community, event, or situation.

It is a qualitative research approach that aims to provide a detailed and comprehensive understanding of the case being studied. Case studies typically involve multiple sources of data, including interviews, observations, documents, and artifacts, which are analyzed using various techniques, such as content analysis, thematic analysis, and grounded theory. The findings of a case study are often used to develop theories, inform policy or practice, or generate new research questions.

Types of Case Study

Types and Methods of Case Study are as follows:

Single-Case Study

A single-case study is an in-depth analysis of a single case. This type of case study is useful when the researcher wants to understand a specific phenomenon in detail.

For Example , A researcher might conduct a single-case study on a particular individual to understand their experiences with a particular health condition or a specific organization to explore their management practices. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a single-case study are often used to generate new research questions, develop theories, or inform policy or practice.

Multiple-Case Study

A multiple-case study involves the analysis of several cases that are similar in nature. This type of case study is useful when the researcher wants to identify similarities and differences between the cases.

For Example, a researcher might conduct a multiple-case study on several companies to explore the factors that contribute to their success or failure. The researcher collects data from each case, compares and contrasts the findings, and uses various techniques to analyze the data, such as comparative analysis or pattern-matching. The findings of a multiple-case study can be used to develop theories, inform policy or practice, or generate new research questions.

Exploratory Case Study

An exploratory case study is used to explore a new or understudied phenomenon. This type of case study is useful when the researcher wants to generate hypotheses or theories about the phenomenon.

For Example, a researcher might conduct an exploratory case study on a new technology to understand its potential impact on society. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as grounded theory or content analysis. The findings of an exploratory case study can be used to generate new research questions, develop theories, or inform policy or practice.

Descriptive Case Study

A descriptive case study is used to describe a particular phenomenon in detail. This type of case study is useful when the researcher wants to provide a comprehensive account of the phenomenon.

For Example, a researcher might conduct a descriptive case study on a particular community to understand its social and economic characteristics. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a descriptive case study can be used to inform policy or practice or generate new research questions.

Instrumental Case Study

An instrumental case study is used to understand a particular phenomenon that is instrumental in achieving a particular goal. This type of case study is useful when the researcher wants to understand the role of the phenomenon in achieving the goal.

For Example, a researcher might conduct an instrumental case study on a particular policy to understand its impact on achieving a particular goal, such as reducing poverty. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of an instrumental case study can be used to inform policy or practice or generate new research questions.

Case Study Data Collection Methods

Here are some common data collection methods for case studies:

Interviews involve asking questions to individuals who have knowledge or experience relevant to the case study. Interviews can be structured (where the same questions are asked to all participants) or unstructured (where the interviewer follows up on the responses with further questions). Interviews can be conducted in person, over the phone, or through video conferencing.

Observations

Observations involve watching and recording the behavior and activities of individuals or groups relevant to the case study. Observations can be participant (where the researcher actively participates in the activities) or non-participant (where the researcher observes from a distance). Observations can be recorded using notes, audio or video recordings, or photographs.

Documents can be used as a source of information for case studies. Documents can include reports, memos, emails, letters, and other written materials related to the case study. Documents can be collected from the case study participants or from public sources.

Surveys involve asking a set of questions to a sample of individuals relevant to the case study. Surveys can be administered in person, over the phone, through mail or email, or online. Surveys can be used to gather information on attitudes, opinions, or behaviors related to the case study.

Artifacts are physical objects relevant to the case study. Artifacts can include tools, equipment, products, or other objects that provide insights into the case study phenomenon.

How to conduct Case Study Research

Conducting a case study research involves several steps that need to be followed to ensure the quality and rigor of the study. Here are the steps to conduct case study research:

  • Define the research questions: The first step in conducting a case study research is to define the research questions. The research questions should be specific, measurable, and relevant to the case study phenomenon under investigation.
  • Select the case: The next step is to select the case or cases to be studied. The case should be relevant to the research questions and should provide rich and diverse data that can be used to answer the research questions.
  • Collect data: Data can be collected using various methods, such as interviews, observations, documents, surveys, and artifacts. The data collection method should be selected based on the research questions and the nature of the case study phenomenon.
  • Analyze the data: The data collected from the case study should be analyzed using various techniques, such as content analysis, thematic analysis, or grounded theory. The analysis should be guided by the research questions and should aim to provide insights and conclusions relevant to the research questions.
  • Draw conclusions: The conclusions drawn from the case study should be based on the data analysis and should be relevant to the research questions. The conclusions should be supported by evidence and should be clearly stated.
  • Validate the findings: The findings of the case study should be validated by reviewing the data and the analysis with participants or other experts in the field. This helps to ensure the validity and reliability of the findings.
  • Write the report: The final step is to write the report of the case study research. The report should provide a clear description of the case study phenomenon, the research questions, the data collection methods, the data analysis, the findings, and the conclusions. The report should be written in a clear and concise manner and should follow the guidelines for academic writing.

Examples of Case Study

Here are some examples of case study research:

  • The Hawthorne Studies : Conducted between 1924 and 1932, the Hawthorne Studies were a series of case studies conducted by Elton Mayo and his colleagues to examine the impact of work environment on employee productivity. The studies were conducted at the Hawthorne Works plant of the Western Electric Company in Chicago and included interviews, observations, and experiments.
  • The Stanford Prison Experiment: Conducted in 1971, the Stanford Prison Experiment was a case study conducted by Philip Zimbardo to examine the psychological effects of power and authority. The study involved simulating a prison environment and assigning participants to the role of guards or prisoners. The study was controversial due to the ethical issues it raised.
  • The Challenger Disaster: The Challenger Disaster was a case study conducted to examine the causes of the Space Shuttle Challenger explosion in 1986. The study included interviews, observations, and analysis of data to identify the technical, organizational, and cultural factors that contributed to the disaster.
  • The Enron Scandal: The Enron Scandal was a case study conducted to examine the causes of the Enron Corporation’s bankruptcy in 2001. The study included interviews, analysis of financial data, and review of documents to identify the accounting practices, corporate culture, and ethical issues that led to the company’s downfall.
  • The Fukushima Nuclear Disaster : The Fukushima Nuclear Disaster was a case study conducted to examine the causes of the nuclear accident that occurred at the Fukushima Daiichi Nuclear Power Plant in Japan in 2011. The study included interviews, analysis of data, and review of documents to identify the technical, organizational, and cultural factors that contributed to the disaster.

Application of Case Study

Case studies have a wide range of applications across various fields and industries. Here are some examples:

Business and Management

Case studies are widely used in business and management to examine real-life situations and develop problem-solving skills. Case studies can help students and professionals to develop a deep understanding of business concepts, theories, and best practices.

Case studies are used in healthcare to examine patient care, treatment options, and outcomes. Case studies can help healthcare professionals to develop critical thinking skills, diagnose complex medical conditions, and develop effective treatment plans.

Case studies are used in education to examine teaching and learning practices. Case studies can help educators to develop effective teaching strategies, evaluate student progress, and identify areas for improvement.

Social Sciences

Case studies are widely used in social sciences to examine human behavior, social phenomena, and cultural practices. Case studies can help researchers to develop theories, test hypotheses, and gain insights into complex social issues.

Law and Ethics

Case studies are used in law and ethics to examine legal and ethical dilemmas. Case studies can help lawyers, policymakers, and ethical professionals to develop critical thinking skills, analyze complex cases, and make informed decisions.

Purpose of Case Study

The purpose of a case study is to provide a detailed analysis of a specific phenomenon, issue, or problem in its real-life context. A case study is a qualitative research method that involves the in-depth exploration and analysis of a particular case, which can be an individual, group, organization, event, or community.

The primary purpose of a case study is to generate a comprehensive and nuanced understanding of the case, including its history, context, and dynamics. Case studies can help researchers to identify and examine the underlying factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and detailed understanding of the case, which can inform future research, practice, or policy.

Case studies can also serve other purposes, including:

  • Illustrating a theory or concept: Case studies can be used to illustrate and explain theoretical concepts and frameworks, providing concrete examples of how they can be applied in real-life situations.
  • Developing hypotheses: Case studies can help to generate hypotheses about the causal relationships between different factors and outcomes, which can be tested through further research.
  • Providing insight into complex issues: Case studies can provide insights into complex and multifaceted issues, which may be difficult to understand through other research methods.
  • Informing practice or policy: Case studies can be used to inform practice or policy by identifying best practices, lessons learned, or areas for improvement.

Advantages of Case Study Research

There are several advantages of case study research, including:

  • In-depth exploration: Case study research allows for a detailed exploration and analysis of a specific phenomenon, issue, or problem in its real-life context. This can provide a comprehensive understanding of the case and its dynamics, which may not be possible through other research methods.
  • Rich data: Case study research can generate rich and detailed data, including qualitative data such as interviews, observations, and documents. This can provide a nuanced understanding of the case and its complexity.
  • Holistic perspective: Case study research allows for a holistic perspective of the case, taking into account the various factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and comprehensive understanding of the case.
  • Theory development: Case study research can help to develop and refine theories and concepts by providing empirical evidence and concrete examples of how they can be applied in real-life situations.
  • Practical application: Case study research can inform practice or policy by identifying best practices, lessons learned, or areas for improvement.
  • Contextualization: Case study research takes into account the specific context in which the case is situated, which can help to understand how the case is influenced by the social, cultural, and historical factors of its environment.

Limitations of Case Study Research

There are several limitations of case study research, including:

  • Limited generalizability : Case studies are typically focused on a single case or a small number of cases, which limits the generalizability of the findings. The unique characteristics of the case may not be applicable to other contexts or populations, which may limit the external validity of the research.
  • Biased sampling: Case studies may rely on purposive or convenience sampling, which can introduce bias into the sample selection process. This may limit the representativeness of the sample and the generalizability of the findings.
  • Subjectivity: Case studies rely on the interpretation of the researcher, which can introduce subjectivity into the analysis. The researcher’s own biases, assumptions, and perspectives may influence the findings, which may limit the objectivity of the research.
  • Limited control: Case studies are typically conducted in naturalistic settings, which limits the control that the researcher has over the environment and the variables being studied. This may limit the ability to establish causal relationships between variables.
  • Time-consuming: Case studies can be time-consuming to conduct, as they typically involve a detailed exploration and analysis of a specific case. This may limit the feasibility of conducting multiple case studies or conducting case studies in a timely manner.
  • Resource-intensive: Case studies may require significant resources, including time, funding, and expertise. This may limit the ability of researchers to conduct case studies in resource-constrained settings.

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Case Study Conclusion

The end is sometimes the most visible piece of academic writing. The conclusion of the case study is an ignored portion. Several students make case study research papers every year on the demand of their tutors. But, very few of them realize the importance of every segment of it. From the introduction to the case study conclusion, every single thing matters. As it’s a matter of your future academic success, it is equally beneficial for the students to craft valuable endings for their case studies.

Students may question themselves about, what makes a brilliant conclusion? Well, there are plenty of rules that should be applied while making one. For example, there are a few things to be kept in mind for writing the introductions. Similarly, extensive research is required to make an impactful conclusion for a case study.

Importance OF A Conclusion In The Case Study For A Student  

It’s a years-long pattern that the last part of any content gets neglected. The reasons are quite clear, either you lose interest in your topic, or you want to finish it in a hurry. But whatever the reason it is, it’s not ideal to ignore the end of your case study solutions writing. Various elements define the importance of the concluding part.

The ending is the most read portion of the content as it summarizes all the vital points of the introduction of your case study. So if you have not paid much attention to your conclusions, there are high chance that your case study will not look impressive.

The Common Sample OF Conclusion And Recommendation In The Case Study 

Students can feasibly go through our site to get samples of the conclusion of a case study. However, the most common things you can find in a case study sample are the proper solutions to your argued problems. Not to forget the requirements of the deep analysis on how to overcome them.

A good case study is nothing without the relevant samples and recommendations. Hence, it’s the most crucial part of the writings to list the proper recommendations for your tutors. Students are advised that all of their suggestions must include specific reports of all the emerging limitations. They can address all of the issues with the possible solutions to them that would be helpful for future work.

It doesn’t matter if you are concluding a long report or a short one. The recommendations should be listed in pointers to avoid any confusion and add more to the clarity.

What Case Study Conclusions Should Look Like?

Your conclusion is the most integral part of your research papers. If a good conclusion has been provided to the case study, there are high chances that your not-so-good point in the middle of the starting sections gets blurred. The conclusion part of the case study that brings closure to your story is the reformed way. All of your researched data can have more impact if the ending part of your case study states the solutions to the key issues.

Example OF The Case Studies Conclusion   

Students can list what they have learned from this particular topic in their conclusion. It can make you wiser in comparison to the next applicant. For example, you can discuss any special category of the users related to the company you are conducting a case study on. You can highlight the new products which they are interested in launching. You can also discuss something that is cutting-edge and advances the boundaries of practice or science.

As you can see, there are various ways by which you can create a lasting impact on your conclusions.

Get Our Help To Write An Impressive Conclusion For Your Case Study

Writing an excellent case study is not an easy task to accomplish. Moreover, its different sections from the beginning to the conclusion demand immense intensity and research. But, we assure our students that our case study writers can deliver quality case studies to you. They are experts in creating unique content. Hence, you can freely rely on our case study services to attain the utmost satisfaction.

How Do You Write A Conclusion?

The conclusion of a case study comprises of the following important steps:

  • Look out for the logical connections.
  • Make sure your conclusion has a direct link to your introduction.
  • Keep the basic logic in mind.
  • Encourage the reader to draw their own conclusions.
  • Provide recommendations.
  • Conclusions should be definite.
  • The recommendations should directly adhere to your conclusion.

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What Is a Case Study?

Weighing the pros and cons of this method of research

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

case study the conclusion

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case study the conclusion

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  • Pros and Cons

What Types of Case Studies Are Out There?

Where do you find data for a case study, how do i write a psychology case study.

A case study is an in-depth study of one person, group, or event. In a case study, nearly every aspect of the subject's life and history is analyzed to seek patterns and causes of behavior. Case studies can be used in many different fields, including psychology, medicine, education, anthropology, political science, and social work.

The point of a case study is to learn as much as possible about an individual or group so that the information can be generalized to many others. Unfortunately, case studies tend to be highly subjective, and it is sometimes difficult to generalize results to a larger population.

While case studies focus on a single individual or group, they follow a format similar to other types of psychology writing. If you are writing a case study, we got you—here are some rules of APA format to reference.  

At a Glance

A case study, or an in-depth study of a person, group, or event, can be a useful research tool when used wisely. In many cases, case studies are best used in situations where it would be difficult or impossible for you to conduct an experiment. They are helpful for looking at unique situations and allow researchers to gather a lot of˜ information about a specific individual or group of people. However, it's important to be cautious of any bias we draw from them as they are highly subjective.

What Are the Benefits and Limitations of Case Studies?

A case study can have its strengths and weaknesses. Researchers must consider these pros and cons before deciding if this type of study is appropriate for their needs.

One of the greatest advantages of a case study is that it allows researchers to investigate things that are often difficult or impossible to replicate in a lab. Some other benefits of a case study:

  • Allows researchers to capture information on the 'how,' 'what,' and 'why,' of something that's implemented
  • Gives researchers the chance to collect information on why one strategy might be chosen over another
  • Permits researchers to develop hypotheses that can be explored in experimental research

On the other hand, a case study can have some drawbacks:

  • It cannot necessarily be generalized to the larger population
  • Cannot demonstrate cause and effect
  • It may not be scientifically rigorous
  • It can lead to bias

Researchers may choose to perform a case study if they want to explore a unique or recently discovered phenomenon. Through their insights, researchers develop additional ideas and study questions that might be explored in future studies.

It's important to remember that the insights from case studies cannot be used to determine cause-and-effect relationships between variables. However, case studies may be used to develop hypotheses that can then be addressed in experimental research.

Case Study Examples

There have been a number of notable case studies in the history of psychology. Much of  Freud's work and theories were developed through individual case studies. Some great examples of case studies in psychology include:

  • Anna O : Anna O. was a pseudonym of a woman named Bertha Pappenheim, a patient of a physician named Josef Breuer. While she was never a patient of Freud's, Freud and Breuer discussed her case extensively. The woman was experiencing symptoms of a condition that was then known as hysteria and found that talking about her problems helped relieve her symptoms. Her case played an important part in the development of talk therapy as an approach to mental health treatment.
  • Phineas Gage : Phineas Gage was a railroad employee who experienced a terrible accident in which an explosion sent a metal rod through his skull, damaging important portions of his brain. Gage recovered from his accident but was left with serious changes in both personality and behavior.
  • Genie : Genie was a young girl subjected to horrific abuse and isolation. The case study of Genie allowed researchers to study whether language learning was possible, even after missing critical periods for language development. Her case also served as an example of how scientific research may interfere with treatment and lead to further abuse of vulnerable individuals.

Such cases demonstrate how case research can be used to study things that researchers could not replicate in experimental settings. In Genie's case, her horrific abuse denied her the opportunity to learn a language at critical points in her development.

This is clearly not something researchers could ethically replicate, but conducting a case study on Genie allowed researchers to study phenomena that are otherwise impossible to reproduce.

There are a few different types of case studies that psychologists and other researchers might use:

  • Collective case studies : These involve studying a group of individuals. Researchers might study a group of people in a certain setting or look at an entire community. For example, psychologists might explore how access to resources in a community has affected the collective mental well-being of those who live there.
  • Descriptive case studies : These involve starting with a descriptive theory. The subjects are then observed, and the information gathered is compared to the pre-existing theory.
  • Explanatory case studies : These   are often used to do causal investigations. In other words, researchers are interested in looking at factors that may have caused certain things to occur.
  • Exploratory case studies : These are sometimes used as a prelude to further, more in-depth research. This allows researchers to gather more information before developing their research questions and hypotheses .
  • Instrumental case studies : These occur when the individual or group allows researchers to understand more than what is initially obvious to observers.
  • Intrinsic case studies : This type of case study is when the researcher has a personal interest in the case. Jean Piaget's observations of his own children are good examples of how an intrinsic case study can contribute to the development of a psychological theory.

The three main case study types often used are intrinsic, instrumental, and collective. Intrinsic case studies are useful for learning about unique cases. Instrumental case studies help look at an individual to learn more about a broader issue. A collective case study can be useful for looking at several cases simultaneously.

The type of case study that psychology researchers use depends on the unique characteristics of the situation and the case itself.

There are a number of different sources and methods that researchers can use to gather information about an individual or group. Six major sources that have been identified by researchers are:

  • Archival records : Census records, survey records, and name lists are examples of archival records.
  • Direct observation : This strategy involves observing the subject, often in a natural setting . While an individual observer is sometimes used, it is more common to utilize a group of observers.
  • Documents : Letters, newspaper articles, administrative records, etc., are the types of documents often used as sources.
  • Interviews : Interviews are one of the most important methods for gathering information in case studies. An interview can involve structured survey questions or more open-ended questions.
  • Participant observation : When the researcher serves as a participant in events and observes the actions and outcomes, it is called participant observation.
  • Physical artifacts : Tools, objects, instruments, and other artifacts are often observed during a direct observation of the subject.

If you have been directed to write a case study for a psychology course, be sure to check with your instructor for any specific guidelines you need to follow. If you are writing your case study for a professional publication, check with the publisher for their specific guidelines for submitting a case study.

Here is a general outline of what should be included in a case study.

Section 1: A Case History

This section will have the following structure and content:

Background information : The first section of your paper will present your client's background. Include factors such as age, gender, work, health status, family mental health history, family and social relationships, drug and alcohol history, life difficulties, goals, and coping skills and weaknesses.

Description of the presenting problem : In the next section of your case study, you will describe the problem or symptoms that the client presented with.

Describe any physical, emotional, or sensory symptoms reported by the client. Thoughts, feelings, and perceptions related to the symptoms should also be noted. Any screening or diagnostic assessments that are used should also be described in detail and all scores reported.

Your diagnosis : Provide your diagnosis and give the appropriate Diagnostic and Statistical Manual code. Explain how you reached your diagnosis, how the client's symptoms fit the diagnostic criteria for the disorder(s), or any possible difficulties in reaching a diagnosis.

Section 2: Treatment Plan

This portion of the paper will address the chosen treatment for the condition. This might also include the theoretical basis for the chosen treatment or any other evidence that might exist to support why this approach was chosen.

  • Cognitive behavioral approach : Explain how a cognitive behavioral therapist would approach treatment. Offer background information on cognitive behavioral therapy and describe the treatment sessions, client response, and outcome of this type of treatment. Make note of any difficulties or successes encountered by your client during treatment.
  • Humanistic approach : Describe a humanistic approach that could be used to treat your client, such as client-centered therapy . Provide information on the type of treatment you chose, the client's reaction to the treatment, and the end result of this approach. Explain why the treatment was successful or unsuccessful.
  • Psychoanalytic approach : Describe how a psychoanalytic therapist would view the client's problem. Provide some background on the psychoanalytic approach and cite relevant references. Explain how psychoanalytic therapy would be used to treat the client, how the client would respond to therapy, and the effectiveness of this treatment approach.
  • Pharmacological approach : If treatment primarily involves the use of medications, explain which medications were used and why. Provide background on the effectiveness of these medications and how monotherapy may compare with an approach that combines medications with therapy or other treatments.

This section of a case study should also include information about the treatment goals, process, and outcomes.

When you are writing a case study, you should also include a section where you discuss the case study itself, including the strengths and limitiations of the study. You should note how the findings of your case study might support previous research. 

In your discussion section, you should also describe some of the implications of your case study. What ideas or findings might require further exploration? How might researchers go about exploring some of these questions in additional studies?

Need More Tips?

Here are a few additional pointers to keep in mind when formatting your case study:

  • Never refer to the subject of your case study as "the client." Instead, use their name or a pseudonym.
  • Read examples of case studies to gain an idea about the style and format.
  • Remember to use APA format when citing references .

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach .  BMC Med Res Methodol . 2011;11:100.

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach . BMC Med Res Methodol . 2011 Jun 27;11:100. doi:10.1186/1471-2288-11-100

Gagnon, Yves-Chantal.  The Case Study as Research Method: A Practical Handbook . Canada, Chicago Review Press Incorporated DBA Independent Pub Group, 2010.

Yin, Robert K. Case Study Research and Applications: Design and Methods . United States, SAGE Publications, 2017.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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  • Knowledge Base
  • How to conclude an essay | Interactive example

How to Conclude an Essay | Interactive Example

Published on January 24, 2019 by Shona McCombes . Revised on July 23, 2023.

The conclusion is the final paragraph of your essay . A strong conclusion aims to:

  • Tie together the essay’s main points
  • Show why your argument matters
  • Leave the reader with a strong impression

Your conclusion should give a sense of closure and completion to your argument, but also show what new questions or possibilities it has opened up.

This conclusion is taken from our annotated essay example , which discusses the history of the Braille system. Hover over each part to see why it’s effective.

Braille paved the way for dramatic cultural changes in the way blind people were treated and the opportunities available to them. Louis Braille’s innovation was to reimagine existing reading systems from a blind perspective, and the success of this invention required sighted teachers to adapt to their students’ reality instead of the other way around. In this sense, Braille helped drive broader social changes in the status of blindness. New accessibility tools provide practical advantages to those who need them, but they can also change the perspectives and attitudes of those who do not.

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Table of contents

Step 1: return to your thesis, step 2: review your main points, step 3: show why it matters, what shouldn’t go in the conclusion, more examples of essay conclusions, other interesting articles, frequently asked questions about writing an essay conclusion.

To begin your conclusion, signal that the essay is coming to an end by returning to your overall argument.

Don’t just repeat your thesis statement —instead, try to rephrase your argument in a way that shows how it has been developed since the introduction.

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Next, remind the reader of the main points that you used to support your argument.

Avoid simply summarizing each paragraph or repeating each point in order; try to bring your points together in a way that makes the connections between them clear. The conclusion is your final chance to show how all the paragraphs of your essay add up to a coherent whole.

To wrap up your conclusion, zoom out to a broader view of the topic and consider the implications of your argument. For example:

  • Does it contribute a new understanding of your topic?
  • Does it raise new questions for future study?
  • Does it lead to practical suggestions or predictions?
  • Can it be applied to different contexts?
  • Can it be connected to a broader debate or theme?

Whatever your essay is about, the conclusion should aim to emphasize the significance of your argument, whether that’s within your academic subject or in the wider world.

Try to end with a strong, decisive sentence, leaving the reader with a lingering sense of interest in your topic.

The easiest way to improve your conclusion is to eliminate these common mistakes.

Don’t include new evidence

Any evidence or analysis that is essential to supporting your thesis statement should appear in the main body of the essay.

The conclusion might include minor pieces of new information—for example, a sentence or two discussing broader implications, or a quotation that nicely summarizes your central point. But it shouldn’t introduce any major new sources or ideas that need further explanation to understand.

Don’t use “concluding phrases”

Avoid using obvious stock phrases to tell the reader what you’re doing:

  • “In conclusion…”
  • “To sum up…”

These phrases aren’t forbidden, but they can make your writing sound weak. By returning to your main argument, it will quickly become clear that you are concluding the essay—you shouldn’t have to spell it out.

Don’t undermine your argument

Avoid using apologetic phrases that sound uncertain or confused:

  • “This is just one approach among many.”
  • “There are good arguments on both sides of this issue.”
  • “There is no clear answer to this problem.”

Even if your essay has explored different points of view, your own position should be clear. There may be many possible approaches to the topic, but you want to leave the reader convinced that yours is the best one!

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case study the conclusion

  • Argumentative
  • Literary analysis

This conclusion is taken from an argumentative essay about the internet’s impact on education. It acknowledges the opposing arguments while taking a clear, decisive position.

The internet has had a major positive impact on the world of education; occasional pitfalls aside, its value is evident in numerous applications. The future of teaching lies in the possibilities the internet opens up for communication, research, and interactivity. As the popularity of distance learning shows, students value the flexibility and accessibility offered by digital education, and educators should fully embrace these advantages. The internet’s dangers, real and imaginary, have been documented exhaustively by skeptics, but the internet is here to stay; it is time to focus seriously on its potential for good.

This conclusion is taken from a short expository essay that explains the invention of the printing press and its effects on European society. It focuses on giving a clear, concise overview of what was covered in the essay.

The invention of the printing press was important not only in terms of its immediate cultural and economic effects, but also in terms of its major impact on politics and religion across Europe. In the century following the invention of the printing press, the relatively stationary intellectual atmosphere of the Middle Ages gave way to the social upheavals of the Reformation and the Renaissance. A single technological innovation had contributed to the total reshaping of the continent.

This conclusion is taken from a literary analysis essay about Mary Shelley’s Frankenstein . It summarizes what the essay’s analysis achieved and emphasizes its originality.

By tracing the depiction of Frankenstein through the novel’s three volumes, I have demonstrated how the narrative structure shifts our perception of the character. While the Frankenstein of the first volume is depicted as having innocent intentions, the second and third volumes—first in the creature’s accusatory voice, and then in his own voice—increasingly undermine him, causing him to appear alternately ridiculous and vindictive. Far from the one-dimensional villain he is often taken to be, the character of Frankenstein is compelling because of the dynamic narrative frame in which he is placed. In this frame, Frankenstein’s narrative self-presentation responds to the images of him we see from others’ perspectives. This conclusion sheds new light on the novel, foregrounding Shelley’s unique layering of narrative perspectives and its importance for the depiction of character.

If you want to know more about AI tools , college essays , or fallacies make sure to check out some of our other articles with explanations and examples or go directly to our tools!

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Your essay’s conclusion should contain:

  • A rephrased version of your overall thesis
  • A brief review of the key points you made in the main body
  • An indication of why your argument matters

The conclusion may also reflect on the broader implications of your argument, showing how your ideas could applied to other contexts or debates.

For a stronger conclusion paragraph, avoid including:

  • Important evidence or analysis that wasn’t mentioned in the main body
  • Generic concluding phrases (e.g. “In conclusion…”)
  • Weak statements that undermine your argument (e.g. “There are good points on both sides of this issue.”)

Your conclusion should leave the reader with a strong, decisive impression of your work.

The conclusion paragraph of an essay is usually shorter than the introduction . As a rule, it shouldn’t take up more than 10–15% of the text.

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McCombes, S. (2023, July 23). How to Conclude an Essay | Interactive Example. Scribbr. Retrieved February 27, 2024, from https://www.scribbr.com/academic-essay/conclusion/

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  • Open access
  • Published: 26 February 2024

Body mass index stratified meta-analysis of genome-wide association studies of polycystic ovary syndrome in women of European ancestry

  • Kharis Burns 1 , 2 ,
  • Benjamin H. Mullin 3 , 4 ,
  • Loes M. E. Moolhuijsen 5 ,
  • Triin Laisk 6 ,
  • Jaakko S. Tyrmi 7 , 8 ,
  • Jinrui Cui 9 ,
  • Ky’Era V. Actkins 10 , 11 , 12 ,
  • Yvonne V. Louwers 13 ,
  • Estonian Biobank Research Team ,
  • Lea K. Davis 11 , 12 ,
  • Frank Dudbridge 14 ,
  • Ricardo Azziz 15 ,
  • Mark O. Goodarzi 9 ,
  • Hannele Laivuori 7 , 16 , 17 , 18 ,
  • Reedik Mägi 6 ,
  • Jenny A. Visser 5 ,
  • Joop S. E. Laven 13 ,
  • Scott G. Wilson 3 , 4 , 19 ,
  • International PCOS Consortium ,
  • Felix R. Day 20 &
  • Bronwyn G. A. Stuckey 2 , 3 , 21  

BMC Genomics volume  25 , Article number:  208 ( 2024 ) Cite this article

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Polycystic ovary syndrome (PCOS) is a complex multifactorial disorder with a substantial genetic component. However, the clinical manifestations of PCOS are heterogeneous with notable differences between lean and obese women, implying a different pathophysiology manifesting in differential body mass index (BMI). We performed a meta-analysis of genome-wide association study (GWAS) data from six well-characterised cohorts, using a case–control study design stratified by BMI, aiming to identify genetic variants associated with lean and overweight/obese PCOS subtypes.

The study comprised 254,588 women (5,937 cases and 248,651 controls) from individual studies performed in Australia, Estonia, Finland, the Netherlands and United States of America, and separated according to three BMI stratifications (lean, overweight and obese). Genome-wide association analyses were performed for each stratification within each cohort, with the data for each BMI group meta-analysed using METAL software. Almost half of the total study population (47%, n  = 119,584) were of lean BMI (≤ 25 kg/m 2 ). Two genome-wide significant loci were identified for lean PCOS, led by rs12000707 within DENND1A ( P  = 1.55 × 10 –12 ) and rs2228260 within XBP1 ( P  = 3.68 × 10 –8 ). One additional locus, LINC02905 , was highlighted as significantly associated with lean PCOS through gene-based analyses ( P  = 1.76 × 10 –6 ). There were no significant loci observed for the overweight or obese sub-strata when analysed separately, however, when these strata were combined, an association signal led by rs569675099 within DENND1A reached genome-wide significance ( P  = 3.22 × 10 –9 ) and a gene-based association was identified with ERBB4 ( P  = 1.59 × 10 –6 ). Nineteen of 28 signals identified in previous GWAS, were replicated with consistent allelic effect in the lean stratum. There were less replicated signals in the overweight and obese groups, and only 4 SNPs were replicated in each of the three BMI strata.

Conclusions

Genetic variation at the XBP1, LINC02905 and ERBB4 loci were associated with PCOS within unique BMI strata, while DENND1A demonstrated associations across multiple strata, providing evidence of both distinct and shared genetic features between lean and overweight/obese PCOS-affected women. This study demonstrated that PCOS-affected women with contrasting body weight are not only phenotypically distinct but also show variation in genetic architecture; lean PCOS women typically display elevated gonadotrophin ratios, lower insulin resistance, higher androgen levels, including adrenal androgens, and more favourable lipid profiles. Overall, these findings add to the growing body of evidence supporting a genetic basis for PCOS as well as differences in genetic patterns relevant to PCOS BMI-subtype.

Peer Review reports

Polycystic ovary syndrome (PCOS) is a common female endocrinopathy, affecting around 5–15% of women, though its aetiology remains to be fully explained [ 1 ]. Cardinal features include hyperandrogenism, oligoamenorrhoea, and often obesity and hyperinsulinaemia [ 1 , 2 ]. Familial inheritance suggests a genetic basis and genome-wide association studies (GWAS) have identified numerous genetic loci significantly associated with this condition [ 3 , 4 , 5 , 6 , 7 ]. However, the relatively modest number of polymorphisms with robust association data identified to date do not appear to entirely explain the disease aetiology [ 4 ]. Most affected women are overweight or obese, with only 16–30% in the lean to normal BMI range [ 8 , 9 , 10 ]. Indeed, the clinical manifestations of PCOS are notably different between lean and obese women, potentially implying a different pathophysiology associated with differential body mass index (BMI) [ 11 ]. It seems possible that a difference in aetiology is attributable to distinct combinations of genotypes. Improved understanding of the genetic architecture of PCOS subtypes may assist in predicting comorbidity risk, facilitating earlier intervention and tailored patient management. Indeed, principal component analysis has demonstrated clusters of risk factors explaining the variance in PCOS – involving women with i) high BMI, insulin resistance, low high-density lipoprotein and low sex hormone binding globulin, ii) hypertension, elevated low-density lipoprotein and hypertriglyceridemia and iii) a lean PCOS phenotype with elevated luteinizing hormone: follicle stimulating hormone ratio and total testosterone [ 11 ]. The lean PCOS phenotype therefore appears to be distinct, potentially necessitating different treatment paradigms, particularly with respect to traditional lifestyle and weight loss recommendations.

In this meta-analysis of PCOS case–control GWAS data we aimed to analyse genotype differences in women with the syndrome based on BMI stratification thus providing insight into the hypothesis that lean and overweight/obese PCOS phenotypes are genetically distinct.

Characteristics of the cohorts

A total of 254,588 women were included in the meta-analysis, comprising 5,937 PCOS cases and 248,651 controls stratified into BMI subgroups i) BMI ≤ 25 kg/m 2 (lean), ii) BMI 25 to 30 kg/m 2 (overweight), and iii) BMI ≥ 30 kg/m 2 (obese) (Table  1 ). Almost half of the combined study subjects (47%, n  = 119,584) were of lean BMI. The majority of the cases and controls were from Estonian or Finnish datasets, with the remainder comprising American, Australian and Dutch Caucasian subjects (Table  1 ).

  • Meta-analysis

QQ plots for both the SNP and gene-based analyses completed are presented in Supplementary Fig.  1 .

Single-variant based meta-analysis

For the purposes of this study, genetic loci are defined as regions of the genome containing association signals for PCOS. This study identified two genome-wide significant genetic loci ( P  < 5 × 10 –8 ) for lean PCOS ( n  = 2,919 cases and 166,655 controls) on chromosome 9 in DENND1A (led by rs12000707; P  = 1.55 × 10 –12 ) and on chromosome 22 in XBP1 (led by rs2228260; P  = 3.68 × 10 8 ) (Supplementary Fig.  2 and Supplementary Fig.  3 ). There were no genome-wide significant loci identified for the overweight or obese sub-strata when analysed separately. When the overweight and obese groups were combined (i.e., non-lean subjects), one genome-wide significant locus was identified on chromosome 9, also in DENND1A (led by rs569675099; P  = 3.22 × 10 –9 ) (Supplementary Fig.  3 and Supplementary Fig.  4 ). This variant is in moderate linkage disequilibrium (LD) (r 2  = 0.51) with rs12000707 ( P  = 3.72 × 10 –8 ), which was the lead variant in the lean strata meta-analysis. The variant rs569675099 did not meet GW significance in the lean group ( P  = 1.03 × 10 –5 ) though has previously been identified as associated with PCOS in women of European and Han Chinese ancestry [ 3 , 6 ]. Co-localisation analysis [ 12 ] of the GWAS meta-analysis results for the DENND1A locus in the lean and non-lean groups generated a 95.5% posterior probability of co-localised association signals in the two datasets, indicating the presence of a shared causal variant.

The lead variant in the lean PCOS meta-analysis, rs12000707 (Fig.  1 ; Supplementary Table  1 ), is a non-coding intronic variant that has not previously been highlighted by GWAS but does have GTEx data supporting a role as an expression quantitative trait locus (eQTL) in subcutaneous adipose tissue ( DENND1A ; P  = 7.0 × 10 –6 ) [ 13 ]. This locus contained a total of 124 genome-wide significant variants in the results for the lean PCOS meta-analysis. The lead single nucleotide polymorphism (SNP), rs12000707 is in complete LD with rs9696009 (r 2  = 1), previously reported in a GWAS of PCOS conducted in European populations [ 4 ]. Data for this locus from FUMA [ 14 ] analysis illustrates the large size of the region and number of variants at this site in LD (Supplementary Fig.  5 ). Based on this data alone it is not possible to determine which variant(s) are the functional drivers within this LD block. The SNP rs12000707 also demonstrated nominally significant associations in the overweight and obese groups (Supplementary Table  1 ), with meta-analysis of the 3 BMI strata suggesting that there is no significant heterogeneity between the groups (het P  = 0.56).

figure 1

Regional association plots of genome-wide significant loci identified in the lean PCOS meta-analysis. A  9q33.3 ( DENND1A ) and B  22q12.1 ( XBP1 ). Genetic variants are depicted by position (x-axis) together with their meta-analysis P- value (-log10; y-axis). Variants are colour coded according to their LD (r 2 ) with the lead variant. Mb = million bases

The other signal highlighted in the meta-analysis of lean PCOS, on chromosome 22, led by rs2228260, a synonymous SNP in XBP1 (Fig.  1 ; Supplementary Table  1 ), contained a total of 11 genome-wide significant variants Examination of the LD between these variants suggested that they were all likely representative of the same signal (all r 2  = 1). This association signal is part of a large LD block spanning multiple genes including TTC28 , CHEK2 , HSCB , CCDC117 , XBP1 , ZNRF3 and EMID1 . Any one of these genes could be driving the association signal, however publicly available eQTL data from GTEx shows that rs2228260 is an eQTL for CHEK2 (adrenal gland; P  = 8.3 × 10 –7 ) [ 13 ]. This particular variant has not been identified in any previous GWAS. XBP1 has documented involvement in glucose and lipid metabolism, providing a potential biological link with PCOS, where metabolic disturbances including dyslipidaemia and insulin resistance are noted [ 11 ]. However, other genes within this LD block, including both CHEK2 and ZNRF3 , have previously been implicated in PCOS by data from the Finnish and Estonian cohorts analysed in isolation, populations included in this meta-analysis [ 15 ]. Tyrmi et al., highlighted two putative independent causal variants in the checkpoint kinase 2 ( CHEK2 ) gene, which they proposed were the basis of the association [ 15 ]. The lead variant for the CHEK2 locus identified in that study for the Estonian cohort, rs182075939, is not in strong linkage disequilibrium with rs2228260 (r 2  ≤ 0.2) [ 16 ]. Considering this, we performed a conditional analysis for this locus in the lean PCOS meta-analysis using the COJO function of the GCTA package [ 17 ]. After conditioning on the CHEK2 variant rs182075939, the association between rs2228260 and lean PCOS was no longer genome-wide significant ( P cond  = 1.9 × 10 –5 ), and there was a reduction in effect size (conditioned beta = 0.22, reduced from 0.28). Hence it is not possible to establish rs2228260 as an independent association signal. The lead variant for the Finnish cohort, rs145598156 [ 15 ], located closest to ZNRF3 , and rs2228260 are in linkage equilibrium in Europeans (r 2  = 0.0) [ 16 ]. However, it should be noted that rs145598156 is very rare in non-Finnish Europeans (MAF = 0.003), making accurate estimation of LD difficult. The remaining genes within this LD block have no established biological link with PCOS. The variant rs145598156 was not analysed in this study due to its very low frequency.

The significant associations identified in the lean PCOS meta-analysis were examined within each of the contributing cohorts (Supplementary Table  2 ). The Estonian Biobank demonstrated the strongest associations of the six cohorts for the two lead variants, which is not surprising considering that this cohort contributed the largest number of lean PCOS cases to the study, while the Western Australian PCOS research group (WA PCOS) cohort demonstrated the greatest effect size for these two variants.

Genome-wide suggestive associations may represent true associations that have failed to reach the stringent genome-wide significance threshold for various reasons including statistical power, and which could be validated through further replication. Genetic variants meeting the criterion for genome-wide suggestive association with lean PCOS ( P  < 5 × 10 –6 ) are presented in Supplementary Table  1 . A number of these signals have previously been identified in GWAS of PCOS affected women of both European and Chinese ancestry, specifically variants in YAP1 , KRR1 , IRF1 and BLK [ 4 , 5 , 6 , 7 ]. However, there has been no previous research published specifically identifying these loci in lean PCOS affected subjects. Furthermore, from the analysis of the combined overweight/obese cohorts, (Supplementary Table  3 ), genome wide suggestive signals were identified for three previously reported PCOS loci. rs11031006 within FSHB was identified as genome-wide suggestive ( P  = 1.42 × 10 –7 ), which has been previously reported as a risk variant for PCOS [ 5 , 6 , 18 ]. The other signals in known PCOS loci include rs11453664 on chromosome 2 within ERBB4 ( P  = 7.85 × 10 –7 ) and rs3729853 in GATA4 on chromosome 8 ( P  = 2.4 × 10 –6 ). These specific SNPs have not previously been reported as risk variants for PCOS, though the signal reported in GATA4 , rs3729853, is in modest LD with the previously published significant SNP rs804279 (r 2  = 0.36) [ 4 , 16 ]. Two lead variants were shared by the lean and combined overweight/obese PCOS strata, and with consistent allelic effects observed, when examining results that were of at least suggestive association ( P  < 5 × 10 –6 ; Fig.  2 ). These two variants were located in the DENND1A (rs12000707) and GATA4 (rs3729853) loci. However, the other lead variants that were of at least suggestive association for the lean PCOS stratum and the combined overweight/obese PCOS strata were observed to be uniquely represented in only one stratum or the other (Fig.  2 A), suggesting a potential difference in the genetic architecture of lean versus overweight/obese PCOS; the observed effect size of the risk alleles for those lead variants also followed a similar pattern of segregation (Fig.  2 B).

figure 2

Graph of lead variants in the meta-analyses showing at least suggestive association from each locus. A   P -values are shown from the meta-analyses of the lean PCOS strata (x-axis) or the combined overweight/obese PCOS strata (y-axis). Blue symbols show lead variants with at least suggestive association ( P  < 5 × 10 –6 ) in the lean PCOS strata, red symbols show variants with at least suggestive association in the combined overweight/obese PCOS strata and green variants are those with at least suggestive association in both lean PCOS and combined overweight/obese PCOS strata. Lead variants that did not achieve suggestive association fall in the grey region. Dashed lines show the threshold for genome-wide suggestive association ( P  < 5 × 10 –6 ). B  Plot of the effect size (beta ± SE) for the risk allele of lead variants showing at least suggestive association in the lean PCOS strata (blue symbols), combined overweight/obese PCOS strata (red) and variants that show at least suggestive association in both the lean PCOS and combined overweight/obese PCOS strata (green). Dashed line shows the diagonal

Gene-based association testing

Gene-based association tests are commonly used following single-variant GWAS analysis to model the sum of the effects of all variants within a gene to determine if, despite individual variants not achieving significance, there is statistical evidence of a composite association signal. Gene-based association testing identified two significant associations in the lean PCOS group at the multiple testing corrected (Bonferroni) significance threshold ( P  < 1.96 × 10 –6 ) (Supplementary Fig.  6 ). The leading signal was again DENND1A on chromosome 9 ( P  = 4.04 × 10 –10 ) followed by LINC02905 (also known as C8orf49 ) ( P  = 1.76 × 10 –6 ), a long intergenic non-protein coding RNA gene located between GATA4 and NEIL2 on chromosome 8. The GATA4 / NEIL2 locus has been identified as associated with PCOS in previous GWAS in European populations, with heterogeneous effects depending on diagnostic criteria applied [ 4 ]. The GATA4 / NEIL2 locus also has previous links with ovulatory dysfunction and polycystic ovary morphology [ 4 ]. Accordingly, LINC02905 may be part of a PCOS-susceptibility gene cluster on chromosome 8.

There were no significant gene-based association signals identified for the overweight or obese groups when examined separately, though when combined, one significant signal was identified on chromosome 2 for ERBB4 ( P  = 1.59 × 10 –6 ; Supplementary Fig.  7 ). This gene has previously been identified in GWAS as associated with PCOS, in women of both European and Chinese ancestry [ 4 , 19 , 20 ].

Replication of established PCOS loci

All loci associated with PCOS identified in the previously published PCOS GWAS [ 3 , 4 , 5 , 6 , 7 ] were investigated within each of the three BMI strata (Supplementary Table  4 ). Each locus was examined and observation of P  < 0.05 in any strata of this meta-analysis was considered nominally significant in terms of replication. For any known loci demonstrating nominal association within the cohort, the beta value or odds ratio was checked for consistent allelic direction of effect with that previously reported. All SNPs known to be associated with PCOS through GWAS were analysed in this study with differing levels of significance across the three BMI strata.

Nineteen of these 28 signals were replicated in the lean cohort, demonstrating consistent allelic effect. There were fewer signals replicated in the overweight and obese groups, with 9 and 7 signals respectively with consistent allelic effect. Only four SNPs, rs9696009 within DENND1A, rs2178575 within ERBB4 , rs11031005 within ARL14EP/FSHB and rs1795379 within KRR1 were replicated in all three BMI strata. The signal within DENND1A was most significant in the lean group. The other previously identified SNP in DENND1A , rs2479106, did not meet criteria for replication in any BMI tier. The signal within KRR1 was also most significant in the lean group. The signals in ERBB4 and ARL14EP/FSHB showed similar significance across all BMI strata.

This study aimed to identify differences in genetic architecture between lean, overweight and obese PCOS affected patients in order to provide further insight into potential differences in aetiology between these diverse phenotypes. Single-variant based analysis found evidence of two genome-wide significant genetic associations with the lean phenotype, and one significant association when the overweight and obese groups were combined. Gene-based testing confirmed two genes associated with the lean PCOS group, and one gene associated with the overweight and obese groups combined. Additional variants that demonstrated genome-wide suggestive association were observed in the strata, with lead variants for the lean and combined overweight/obese PCOS strata typically demonstrating greater effects in only one stratum (Figs.  2 A, B), therefore, these data may suggest a difference in the genetic architecture underlying lean versus overweight/obese PCOS.

The strongest association signal in the lean analysis, led by rs12000707 on chromosome 9, is located in DENND1A , which has robust evidence for genetic involvement in PCOS [ 4 ]. This gene encodes the protein DENN/MADD domain containing 1A, which plays a role in endocytosis and receptor turnover and has been identified as associated with PCOS in a number of previous GWAS involving women of European and Han Chinese ancestry [ 3 , 4 ]. Replication studies have further supported these findings, with certain SNPs identified as associated with increased PCOS risk, highlighting it as one of the most well recognised genes implicated in PCOS [ 3 , 4 , 20 ]. Variants within DENND1A have also been associated with hyperandrogenism and ovulatory dysfunction [ 4 , 21 ]. Functional studies have shown the involvement of DENND1A in the pathophysiology of PCOS phenotypes, with laboratory studies demonstrating that ovarian thecal cells in PCOS affected women secrete higher androgen amounts than those from non-affected women, potentially related to upregulation of enzymatic activity in steroid pathways [ 22 ]. A DENND1A isoform, termed DENND1A.V2, has been implicated in the increased expression of genes CYP17A1 and CYP11A1 , which both play a role in the formation of key enzymes involved in androgen steroidogenesis [ 23 ]. This is thought to play a role in PCOS thecal cell androgen production, a feature of PCOS [ 23 ]. Furthermore, forced expression of this DENND1A.V2 isoform in normal human theca cells has been shown to increase androgen and progesterone production, thus converting the normal theca cell into a PCOS phenotype [ 23 ]. Conversely, a knockdown model whereby DENND1A.V2 expression was silenced in PCOS theca cells demonstrated a reduction in steroidogenesis [ 23 ]. A model creating transgenic hDENND1A.V2 mice lines has further demonstrated these concepts; elevation of both ovarian and adrenal Cyp17a1 mRNA levels as well as transgenic ovarian thecal cell steroid production was observed in those mice expressing hDENND1A.V2 transcripts demonstrating impacts on both ovarian and adrenal steroidogenesis [ 24 ].

Rare variants within DENND1A , identified through whole genome sequencing techniques, have also been found to be associated with certain quantitative traits within PCOS-affected women, specifically higher luteinising hormone (LH): follicle stimulating hormone (FSH) ratios [ 25 ]. Clustering analysis, demonstrating ‘reproductive’ and ‘metabolic’ PCOS subgroups, has demonstrated carriers of rare variants in DENND1A were more likely to have a reproductive subtype, characterised by lower BMI and insulin levels and higher LH and sex hormone binding globulin levels [ 26 ]. The finding of a strong association and large effect size for rs12000707 in the lean PCOS strata with DENND1A warrants further investigation. This builds on recent findings of specific DENND1A variants being more prevalent within a reproductive PCOS phenotype, with lower BMI [ 26 ]. Further studies are necessary to replicate these signals and explore the biology of this gene in PCOS subtypes.

The other genome-wide significant signal in the lean study, led by rs2228260, was located on chromosome 22, within XBP1. This signal is composed of a large block of genetic variants in strong LD spanning multiple genes, any one of which could be the effector gene. The SNP identified at this locus is a synonymous coding variant i.e., a codon change that does not alter the encoded amino acid [ 27 ]. Synonymous coding variants are not generally regarded as the most likely effectors for transcriptional regulation or altered protein function, but nevertheless, can have effects on protein expression and function. Previously considered ‘silent’ variants, it is now appreciated that these variants can affect mRNA stability and structure, protein folding, conformation and function [ 28 , 29 ]. Alternatively, this variant may simply be tagging a functional variant that is yet to be identified.

The product of the X-box binding protein 1 ( XBP1 ) gene is a transcription factor involved in the ‘Unfolded Protein Response’ (UPR), a series of finely tuned homoeostatic mechanisms triggered by stress within the endoplasmic reticulum (ER) [ 30 ]. Dysfunctional ER response has been highlighted as a contributor to the pathogenesis of metabolic disease such as type 2 diabetes, obesity and atherosclerotic cardiovascular disease [ 30 ]. Components of the UPR are also known to be involved in the upregulation of metabolic processes, including gluconeogenesis and lipid synthesis, which can be perturbed in PCOS [ 30 ]. The protein product of XBP1 may alter adipocyte, hepatocyte and pancreatic cell signalling pathways to regulate glucose homeostasis and improve insulin sensitivity [ 30 , 31 , 32 ]. Deficiency of XBP1 in pancreatic alpha and beta cells has been implicated in impaired insulin secretion and signalling [ 32 ]. Increased UPR gene expression has also been seen in granulosa cells in PCOS-affected women and these processes, involving ER stress and associated adaptational mechanisms, have been highlighted as regulators of ovarian physiological and pathophysiological outcomes [ 33 ].

XBP1 levels have been reported as higher in women with PCOS [ 34 ]. A recent study examining XBP1 levels in three study groups of women: obese PCOS patients, non-obese PCOS patients and normal weight controls, found significantly higher levels in PCOS patients. Comparison between obese and non-obese PCOS affected women found higher levels in the former group and a significant positive correlation was seen between XBP1 levels and BMI, waist circumference, fasting plasma glucose and triglyceride levels [ 34 ]. In this context, links with obese PCOS and metabolic characteristics mean that the biological effects of XBP1 in the lean phenotype are not immediately obvious and merit further research. Overall, XBP1 appears to be involved in several processes that are perturbed in PCOS patients including oocyte maturation and aberrant glucose and lipid metabolism. Involvement in the lean phenotype appears to be a novel observation based on the literature to date and warrants further study.

Whilst our top lean PCOS SNP on chromosome 22, rs2228260, is located within XBP1 , other genes in the region may also be of relevance to this association signal. CHEK2, or Checkpoint Kinase 2, is one of 7 other genes at this locus harbouring variants in strong LD with rs2228260, and has been associated with PCOS in Finnish and Estonian cohorts [ 15 ]. Indeed, rs2228260 has been reported as an eQTL for CHEK2 in adrenal gland tissue [ 13 ]. Furthermore, existing research reporting an association between this gene and PCOS found that it remained significant in the Finnish population after including BMI as a covariate [ 15 ]. Given the notable proportion of subjects from these cohorts included in this meta-analysis, it is perhaps unsurprising that this signal is present. It should be noted however that the lead SNP identified in this study differs from that reported in the previous Finnish/Estonian research (rs182075939), the SNPs are not in particularly strong LD (r 2  < 0.2) [ 16 ] and conditioning on rs182075939 did not completely remove the association for the lead SNP identified in this study (although it was no longer genome-wide significant). A recent GWAS found several variants within CHEK2 to be associated with age at natural menopause (ANM) [ 35 ]. There is some evidence of LD between rs5762852 found in that study and our lead PCOS SNP rs2228260 (r 2  < 0.2, D’ = 1), potentially suggesting shared biology between PCOS and ANM. CHEK2 is involved in a number of reproductive physiological processes concerning oocyte numbers, follicle atresia, later age at menopause and anti-mullerian hormone (AMH) levels, providing plausible biological links to PCOS [ 35 , 36 ]. It is possible that there is more than one gene in this chromosomal region driving the associations seen in this and previous studies.

Among the genome-wide suggestive lean PCOS loci, YAP1 , KRR1 , IRF1 and BLK are of particular interest. The identification of variants meeting criteria for genome-wide suggestive association with lean PCOS within genes that have previous links to PCOS is encouraging and supports the validity of results. These signals have association with PCOS itself as well as traits involved including ovulatory dysfunction and insulin signalling [ 4 , 37 ]. Polycystic ovary morphology is also associated with some of these signals, specifically with YAP1 [ 4 ]. Interestingly, the two variants in YAP1 previously identified as associated with PCOS, rs1894116 and rs11225154 [ 4 , 7 ] both demonstrated genome-wide suggestive associations in the lean PCOS group but did not reach even nominal significance in the overweight or obese groups. This could suggest that the associations previously reported between this locus and PCOS may be driven primarily by lean PCOS patients. YAP1 (Yes-associated protein 1) has been linked to PCOS pathogenesis through its role in maintaining normal ovarian function, response to gonadotrophins and susceptibility to the effects of androgens [ 38 ]. It is involved in a signalling cascade necessary for ovarian function and ovulation, and previous research has supported a YAP1 mediated mechanism for cell survival and differentiation of granulosa cells during ovulation [ 39 ]. This may suggest that this gene contributes to oligoamenorrhoea, and resultant infertility seen in PCOS.

There were 18 SNPs meeting genome wide suggestive association with the combined overweight and obese PCOS strata. Among these, the TEX41 (testis expressed 41) gene is a non-coding RNA gene, and has been identified as a locus associated with circulating AMH levels in women [ 40 ]. The SNP found to be associated with AMH levels, rs13009019, is in strong LD in Europeans (r 2  = 0.81) with the SNP identified in this study, rs813684 [ 16 ], and is thus likely representative of the same signal. On chromosome 22, rs9613552 is found within the gene TTC28-AS1 (TTC28-Antisense RNA 1). This long non-coding RNA gene has been shown to be downregulated in type 2 diabetes and decreased expression is potentially related to higher risk of developing type 2 diabetes [ 41 ]. CDH18 (cadherin 18 type 2) is one of the closest genes to rs77388455 on chromosome 5. This gene has been reported as associated with phenotypic characteristics common to metabolic syndrome and therefore PCOS, including insulin resistance, glucose intolerance, type 2 diabetes mellitus (T2DM) and obesity [ 42 ] . The top SNP for this gene had a much lower P -value and greater effect size in the non-lean cohort relative to the lean group ( P  = 9.01 × 10 –7 vs. P  = 0.64, and beta 0.39 vs 0.03, respectively). Given the increased propensity for PCOS affected women to develop T2DM, and the associated metabolic syndrome type clinical features, it is possible that CDH18 has some link to PCOS, particularly overweight/obese PCOS. Although signals meeting GW significance were also identified in the overweight/obese groups combined, including DENND1A , the strength of association was lower than that seen in the lean cohort. This may imply that PCOS in overweight/obese women is influenced by environment as well as by genetics. Weight gain and high BMI are associated with PCOS-like features such as insulin resistance and oligoamenorrhoea [ 43 , 44 ]. It is possible that in a proportion of overweight/obese women the strength of the association with genetics is diluted by environmental factors. The relationship between obesity and genetics also needs to be considered, whereby obesity may be regarded as an environmental modifier of PCOS, affecting the emergence of an underlying genetic predisposition as body weight increases.

The gene-based analysis in this study found LINC02905 to be significantly associated with lean PCOS, in addition to DENND1A. LINC02905 is a small uncharacterised gene located in between GATA4 and NEIL2 in a well-established PCOS susceptibility locus. LINC02905 is also known as GATA4 downstream membrane gene ( G4DM ) and is considered to be one of the target genes of GATA4 [ 45 ]. GATA4 (Gata Binding Protein 4) encodes a member of the GATA family of zinc-finger transcription factors, which is thought to play a role in embryogenesis, myocardial differentiation and function and normal testicular development [ 46 ]. Alterations in the expression of GATA4 have been associated with different types of cancer, including ovarian cancer [ 45 , 46 ]. Interestingly, this locus has shown heterogeneity of effect in previous research when analyses were compared according to PCOS subtypes, based on different diagnostic criteria. This signal showed stronger association with PCOS defined by NIH criteria (i.e., hyperandrogenism and oligoamenorrhoea) [ 4 ].

The other gene highlighted in gene-based analyses was ERBB4 (v-erb-a erythroblastic leukemia viral oncogene), which was found to be associated with PCOS in the combined overweight/obese group. This gene has previously been associated with PCOS in both women of European ancestry and Han Chinese women [ 4 , 20 ]. ERBB4 is a member of the tyrosine protein kinase family and epidermal growth factor receptor subfamily. This gene has been associated with both ovulatory dysfunction and polycystic ovarian morphology, and is hypothesised to be involved in oligoamenorrhoea and infertility aspects of this condition [ 4 , 20 ]. Furthermore, a murine model, involving Erbb4 deletion has demonstrated the emergence of various characteristics seen in PCOS patients, specifically disrupted ovulatory cycles with oligomenorrhoea, obesity and impaired oocyte development. In addition, hormonal disturbances included increases in LH and AMH levels, as well as hyperandrogenism [ 47 ]. These findings suggest that ERBB4 may play a key role in PCOS pathophysiology and this is supported by a demonstrated functional role for this gene in ovarian homeostasis and folliculogenesis [ 47 ]. The association of this locus specifically with overweight/obese PCOS subjects is a novel finding.

All SNPs previously associated with PCOS were found to be nominally associated with PCOS in at least one of the three BMI stratifications included in this study. A higher proportion of SNPs met criteria for replication in the lean group compared to the individual or combined overweight and obese strata. This is unlikely to be purely due to sample size as the lean and non-lean (combined overweight/obese) groups contained comparable numbers. Some of the SNPs replicated within the lean group have been associated with ovulatory dysfunction and hyperandrogenism, supporting the concept that the lean phenotype is typified by hormonal disturbance and ovarian abnormality, as opposed to the overweight/obese phenotype, which may display a predominance of metabolic disturbance, such as insulin resistance. For example, rs2349415 within FSHR has been reported as associated with higher FSH levels as well as ovulatory dysfunction [ 7 , 48 ]. This SNP demonstrated strongest association with PCOS in the lean group, followed by the overweight group and no association in the obese cohort ( P  = 3.99 × 10 –3 , 0.02 and 0.96, respectively). Similarly, SNPs within YAP1, TOX3 and IRF1/RAD50  were only significant in the lean group, and have previous association with ovulatory dysfunction, hyperandrogenism and increased testosterone levels respectively [ 4 , 7 ].

The population used for this study comprised a higher proportion of lean women than is described epidemiologically. PCOS-affected women are mostly overweight or obese, with 16–30% falling into a normal or lean BMI category, though around half of cases in this study were BMI < 25 kg/m 2 . Examination of the different cohorts included in the meta-analysis demonstrated varying proportions of women in the BMI strata. The Western Australian PCOS research group aimed to recruit lean women to the study wherever possible to maximise sample size for this group in genetic research, though the proportion of lean/normal BMI women included was just under one third of the WA cohort. The Estonian and Rotterdam cohorts comprised higher proportions of lean women, with 64% and 55% lean cases included respectively. It is noted that these proportions are different to epidemiological reports, though may, in part, be reflective of obesity epidemiology differences between the various cohorts included. Estonia and The Netherlands are known to have lower rates of obesity than Australia and the United States, with data from the US indicating over one third of women in general are obese, compared to 20% in the Netherlands [ 49 ]. Overall, a higher number of lean women included in the study improves power for analysis. The previous GWAS available in the literature were conducted in women with BMI within the overweight to obese range, based on WHO definitions, hence this study is different to those previously reported and needs to be considered when drawing comparison. The two large studies in Han Chinese women reported mean BMI within the overweight range for Asian populations, ranging 23.28–24.76 between the two studies and discovery and replication cohorts [ 3 , 7 ]. The studies conducted in women of European/Caucasian ethnicity included women classified as overweight or obese, with all cases reported to be BMI > 25 [ 4 , 5 , 6 ].

The results from this study provide further evidence to support the theory of genetic differences between lean and overweight/obese PCOS-affected women. Whilst the exact mechanisms by which these signals are contributing to the pathophysiology of this condition are yet to be elucidated, the locations and proximity to a number of genes previously linked with features of PCOS, including ovulatory dysfunction and aberrant metabolism, intimates their potential involvement. Many of the variants identified in this study were intronic, suggesting that they are exerting an effect through modification or enhancement of transcriptional regulation of genes in close proximity (i.e., most often within 200 kb or less) [ 50 ], thus influencing the differences in expression of phenotype in these subjects. The findings reported in this study are unique and add to the growing body of evidence supporting both a genetic basis for PCOS as well as differences in genetic patterns based on PCOS phenotype.

In this study, a meta-analysis of case–control GWAS data stratified according to BMI was performed. Study subjects were allocated into three groups according to BMI, based on WHO definitions. Lean PCOS was defined by BMI ≤ 25 kg/m 2 , overweight PCOS was defined by BMI > 25—< 30 kg/m 2 and obese PCOS was defined by BMI ≥ 30 kg/m 2 ; control subjects were similarly stratified.

The study subjects used for this analysis were sourced from six separate international cohorts, from the United States of America, Australia, Estonia, Finland and the Netherlands. Each centre recruited PCOS affected women and control subjects of European ancestry or identified them from an existing biobank. For the purposes of study inclusion, PCOS cases were defined according to NIH or Rotterdam criteria, or based on ICD codes and questionnaires (“PCOS coded/self-reported”) depending on the criteria stipulated by each individual centre. Controls were defined as women who did not have a PCOS diagnosis, recruited from population-based samples. Research contributions from the United States of America included the Cedars Sinai ( n  = 359 cases and n  = 276 controls) [ 51 ] and BioVU ( n  = 365 cases and n  = 6535 controls) [ 20 ] cohorts. The Australian cohort was from WA-PCOS ( n  = 271 cases and n  = 2492 controls) [ 18 , 52 ]. The contribution from Estonia was from Estonian Biobank ( n  = 3665 cases and n  = 113,878 controls) [ 15 ]. The cohort from Finland was FinnGen ( n  = 643 cases and n  = 117,794 controls) [ 15 ] and from the Netherlands was the Rotterdam PCOS Cohort, with PCOS cases diagnosed in Erasmus Medical Centre, Rotterdam by thorough standardized screening [ 4 ] and controls provided by the Lifelines Cohort Study ( n  = 634 cases and n  = 7685 controls) [ 53 ] All these participating cohorts have been described in detail previously.

Genotyping, quality control and imputation

Cohort-specific information is summarised in Supplementary Table  5 . Only individuals from European ancestry were included in the meta-analysis, with each cohort performing adjustment for principal components to correct for any population stratification. GWAS was performed for each cohort using either the SAIGE [ 54 ] or SNPTEST [ 55 ] software packages. SAIGE software accounts for imbalance in case control ratios, and uses a random effect model. Summary results were supplied from each cohort for meta-analysis, with quality control of the supplied results files performed using EasyQC [ 56 ].

Meta-analysis was performed using the METAL software [ 57 ]. METAL effectively handles analyses where studies contain disproportionate numbers of cases and controls, thus allowing flexibility, and performs tests for heterogeneity to ensure participating studies demonstrate consistent effects [ 57 ]. Meta-analysis was performed using the METAL software using a fixed effects model weighted by standard error [ 57 ]. METAL effectively handles analyses where studies contain disproportionate numbers of cases and controls, thus allowing flexibility, and performs tests for heterogeneity to ensure participating studies demonstrate consistent effects [ 57 ].

Annotation and bioinformatics analysis of meta-analysis results

Meta-analysis results were annotated using FUMA software [ 14 ]. This platform performs functional mapping and annotation of GWAS results to facilitate interpretation and provide biological context, thus helping to identify causal variants. Both single-variant based annotation and gene-based testing approaches were employed. The FUMA module, SNP2GENE approach, uses submitted GWAS summary statistics to identify lead SNPs and perform functional annotation of all variants in the surrounding genomic regions. Three mapping processes, specifically positional, eQTL and chromatin mapping, work in concert to create a mapped genes table, which in turn is used for the next major function of the FUMA software suite, GENE2FUNC. This process annotates the biological context of these genes thus providing insight into the potential mechanisms of the involved loci [ 14 ]. Conditional analysis of the lean PCOS meta-analysis results was performed using the COJO function of the GCTA package [ 17 ], which uses GWAS summary statistics and estimated LD from a sample population to identify independent association signals within a genetic locus [ 58 ]. The sample genotypes used for LD estimation in the conditional analysis were from the Western Australia cohort. Replication analysis of previously identified PCOS loci was performed for each BMI stratum, with P  < 0.05 considered nominally significant evidence of replication. Beta values/odds ratios were then examined to confirm a consistent allelic effect to that previously reported. Analysis of the linkage disequilibrium (LD) in regions of interest was performed using LDlink (1000 Genomes Project Phase 3 EUR population) [ 16 ]. Expression quantitative trait locus (eQTL) associations were assessed using the GTEx dataset [ 13 ]. Co-localisation analysis of GWAS results was performed using the coloc package in R [ 12 ], which uses a Bayesian framework to calculate posterior probabilities for 5 different scenarios regarding the presence and co-localisation of association signals in two datasets.

Availability of data and materials

The datasets generated and/or analysed during the current study are not publicly available due to embargo instituted by the International PCOS Consortium but are available from the corresponding author on reasonable request.

Abbreviations

  • Body mass index

Genome-wide association study

  • Polycystic ovary syndrome

Luteinising hormone

Follicle stimulating hormone

Sex hormone binding globulin

Endoplasmic reticulum

Unfolded Protein Response

Anti-Müllerian hormone

Foetal oocyte attrition

Ovulatory dysfunction

Gestational diabetes mellitus

Expression quantitative trait locus

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Acknowledgements

This study presents independent research supported by the Sir Charles Gairdner Osborne Park Health Care Group, Department of Health (Western Australia), the National Health and Medical Research Council of Australia, Health National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London and the IoPPN Genomics & Biomarker Core Facility, King’s College London. The views expressed are those of the author(s) and not necessarily those of the organisations listed.

Estonian Biobank—Data analysis was carried out in part in the High-Performance Computing Center of University of Tartu

– FinnGen—We want to acknowledge the participants and investigators of FinnGen study. Following biobanks are acknowledged for delivering biobank samples to FinnGen: Auria Biobank ( www.auria.fi/biopankki ), THL Biobank ( www.thl.fi/biobank ), Helsinki Biobank ( www.helsinginbiopankki.fi ), Biobank Borealis of Northern Finland ( https://www.ppshp.fi/Tutkimus-ja-opetus/Biopankki/Pages/Biobank-Borealis-briefly-in-English.aspx ), Finnish Clinical Biobank Tampere ( www.tays.fi/en-US/Research_and_development/Finnish_Clinical_Biobank_Tampere ), Biobank of Eastern Finland ( www.ita-suomenbiopankki.fi/en ), Central Finland Biobank ( www.ksshp.fi/fi-FI/Potilaalle/Biopankki ), Finnish Red Cross Blood Service Biobank ( www.veripalvelu.fi/verenluovutus/biopankkitoiminta ), Terveystalo Biobank ( www.terveystalo.com/fi/Yritystietoa/Terveystalo-Biopankki/Biopankki/ ) and Arctic Biobank ( https://www.oulu.fi/en/university/faculties-and-units/faculty-medicine/northern-finland-birth-cohorts-and-arctic-biobank ). All Finnish Biobanks are members of BBMRI.fi infrastructure ( www.bbmri.fi ). Finnish Biobank Cooperative -FINBB ( https://finbb.fi/ ) is the coordinator of BBMRI-ERIC operations in Finland. The Finnish biobank data can be accessed through the Fingenious ® services ( https://site.fingenious.fi/en/ ) managed by FINBB.

Lifelines Cohort Study—Lifelines is a multi-disciplinary prospective population-based cohort study examining in a unique three-generation design the health and health-related behaviours of 167,729 persons living in the North of the Netherlands. It employs a broad range of investigative procedures in assessing the biomedical, socio-demographic, behavioural, physical and psychological factors which contribute to the health and disease of the general population, with a special focus on multi-morbidity and complex genetics.

Consortium name

Estonian Biobank Research Team:

Andres Metspalu 1 , Lili Milani 1 , Tõnu Esko 1 , Mari Nelis 1 , Georgi Hudjashov. 1

Estonian Biobank Research Team Affiliations.

1 Estonian Genome Center, Institute of Genomics, University of Tartu, Tartu, Estonia,

See attached Supplementary Table  6 for 2023 FinnGenn Banner Authors.

International PCOS Consortium:

Felix R. Day 1

Tugce Karaderi 2,3

Michelle R. Jones 4

Cindy Meun 5

Chunyan He 6,7

Alex Drong 2

Peter Kraft 8

Nan Lin 6,7

Hongyan Huang 8

Linda Broer 9

Reedik Magi 10

Richa Saxena 11

Jaakko S.Tyrmi 12,13

Triin Laisk 10,14

Andres Metspalu 10

Lili Milani 10

Tõnu Esko 10

Mari Nelis 10

Georgi Hudjashov 10

Margrit Urbanek 15,16

M. Geoffrey Hayes 15,16,17

Gudmar Thorleifsson 18

Juan Fernandez-Tajes 2

Anubha Mahajan 2,19

Kharis A. Burns 20,21

Benjamin H. Mullin 22

Bronwyn G. A. Stuckey 21,22,23

Timothy D. Spector 24

Scott G. Wilson 22,24

Frank Dudbridge 25

Jinrui Cui 26

Mark O. Goodarzi 26

Ky’Era Actkins 27,28,29

Lea K. Davis 28,29

Barbara Obermayer-Pietsch 30

André G. Uitterlinden 9

Verneri Anttila 28,31,32

Benjamin M. Neale ,31,32

Marjo-Riitta Jarvelin 33,34,35,36

Hannele Laivuori 12, 37,38,39

Mark Daly 11,32,39

Bart Fauser 36

Irina Kowalska 40

Loes M.E. Moolhuijsen 9

Yvonne Louwers 5

Jenny A. Visser 9

Marianne Andersen 41

Elisabet Stener-Victorin 42

David Ehrmann 43

Richard S. Legro 44

Andres Salumets 12,45,46,47

Mark I. McCarthy 2,19,48

Laure Morin-Papunen 49

Unnur Thorsteinsdottir 18,50

Kari Stefansson 18,50

The 23andMe Research Team ¶

Unnur Styrkarsdottir 18

John R. B. Perry 1

Andrea Dunaif 15,51

Joop Laven 5

Steve Franks 52

Cecilia M. Lindgren 2,11,53

Corrine K. Welt 54,55

International PCOS Consortium Affiliations.

1 MRC Epidemiology Unit, Cambridge Biomedical Campus, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom

2 The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom

3 Department of Biological Sciences, Faculty of Arts and Sciences, Eastern Mediterranean University, Famagusta, Cyprus

4 Center for Bioinformatics & Functional Genomics, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, United States of America

5 Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands

6 Department of Internal Medicine, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America

7 University of Kentucky Markey Cancer Center, Lexington, Kentucky, United States of America

8 Departments of Epidemiology and Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America

9 Department of Internal Medicine, Section Endocrinology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands

10 Estonian Genome Center, Institute of Genomics, University of Tartu, Tartu, Estonia

11 Broad Institute of Harvard and MIT and Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.

12 Center for Child, Adolescent and Maternal Health Research, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.

13 Center for Life Course Health Research, Faculty of Medicine, University of Oulu, Oulu, Finland.

14 Department of Obstetrics and Gynaecology, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia

15 Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America

16 Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America

17 Department of Anthropology, Northwestern University, Evanston, Illinois, United States of America

18 deCODE genetics/Amgen, Reykjavik, Iceland

19 Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom

20 Department of Endocrinology and Diabetes, Royal Perth Hospital, Perth, WA 6009, Australia.

21 Medical School, University of Western Australia, Nedlands, WA, Australia.

22 Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia

23 Keogh Institute for Medical Research, Nedlands, Western Australia, Australia

24 Department of Twin Research and Genetic Epidemiology, King’s College London, London, United Kingdom

25 Department of Health Sciences, University of Leicester, Leicester, UK.

26 Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California, United States of America

27 Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC.

28 Department of Medicine, Division of Genetic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America

29 Vanderbilt Genomics Institute, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America

30 Division of Endocrinology and Diabetology, Department of Internal Medicine Medical University of Graz, Graz, Austria

31 Stanley Center for Psychiatric Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America

32 Analytic and Translational Genetics Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America

33 Department of Epidemiology and Biostatistics, MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, United Kingdom

34 Center for Life Course Health Research, Faculty of Medicine, University of Oulu, Oulu, Finland

35 Biocenter Oulu, University of Oulu, Oulu, Finland, 31 Unit of Primary Care, Oulu University Hospital, Oulu, Finland

36 Department of Reproductive Medicine and Gynaecology, University Medical Center, Utrecht, The Netherlands

37 Department of Obstetrics and Gynecology, Tampere University Hospital, Tampere, Finland.

38 Medical and Clinical Genetics, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.

39 Institute for Molecular Medicine Finland, FIMM, hiLIFE, University of Helsinki, Helsinki, Finland.

40 Department of Internal Medicine and Metabolic Diseases, Medical University of Białystok, Białystok, Poland

41 Odense University Hospital, University of Southern Denmark, Odense, Denmark

42 Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden

43 Department of Medicine, Section of Adult and Paediatric Endocrinology, Diabetes, and Metabolism, The University of Chicago, Chicago, Illinois, United States of America

44 Department of Obstetrics and Gynecology and Public Health Sciences, Penn State University College of Medicine, Hershey, Pennsylvania, United States of America

45 Competence Centre on Health Technologies, Tartu, Estonia

46 Institute of Bio- and Translational Medicine, University of Tartu, Tartu, Estonia

47 Department of Obstetrics and Gynecology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland

48 Oxford NIHR Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom

49 Department of Obstetrics and Gynecology, University of Oulu and Oulu University Hospital, Medical Research Center, PEDEGO Research Unit, Oulu, Finland

50 Faculty of Medicine, University of Iceland, Reykjavik, Iceland

51 Division of Endocrinology, Diabetes and Bone Disease, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America

52 Institute of Reproductive & Developmental Biology, Department of Surgery & Cancer, Imperial College London, London, United Kingdom

53 Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom

54 Division of Endocrinology, Metabolism and Diabetes, University of Utah, Salt Lake City, Utah, United States of America

55 Reproductive Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts, United States of America.

23andMe Research Team (23andMe, Inc., Mountain View, California, United States of America): Michelle Agee, Babak Alipanahi, Adam Auton, Robert K. Bell, Katarzyna Bryc, Sarah L. Elson, Pierre Fontanillas, Nicholas A. Furlotte, David A. Hinds, Karen E. Huber, Aaron Kleinman, Nadia Kenref. Litterman, Matthew H. McIntyre, Joanna L. Mountain, Elizabeth S. Noblin, Carrie A.M. Northover, Steven J. Pitts, J. Fah Sathirapongsasuti, Olga V. Sazonova, Janie F. Shelton, Suyash Shringarpure, Chao Tian, Joyce Y. Tung, Vladimir Vacic, Catherine H. Wilson.

Cedars Sinai – Mark Goodarzi was supported by the Eris M.Field Chair in Diabetes Research and NIDDK P30-DK063481. Ricardo Azziz was supported by NICHD grants R01-HD29364 and K24-HD01346.

WA-PCOS—This study was supported by a grant from the Sir Charles Gairdner Osborne Park Health Care Group Research Advisory Committee, (Grant number: RAC2019-20/029) and, in part, by funding from the National Health and Medical Research Council of Australia (APP2003629 to B.H.M) and a Department of Health (Western Australia) Merit Award (No. 1186046 to B.H.M).

The Estonian Biobank work was supported by the Estonian Research council grant PRG1911 and by European Union through the European Regional Development Fund Project No. 2014–2020.4.01.15–0012 GENTRANSMED.

The FinnGen project is funded by two grants from Business Finland (HUS 4685/31/2016 and UH 4386/31/2016) and the following industry partners: AbbVie Inc., AstraZeneca UK Ltd, Biogen MA Inc., Bristol Myers Squibb (and Celgene Corporation & Celgene International II Sarl), Genentech Inc., Merck Sharp & Dohme Corp., Pfizer Inc., GlaxoSmithKline Intellectual Property Development Ltd., Sanofi US Services Inc., Maze Therapeutics Inc., Janssen Biotech Inc, Novartis AG, and Boehringer Ingelheim International GmbH.

The Lifelines Cohort Study "The Lifelines initiative has been made possible by subsidy from the Dutch Ministry of Health, Welfare and Sport, the Dutch Ministry of Economic Affairs, the University Medical Center Groningen (UMCG), Groningen University and the Provinces in the North of the Netherlands (Drenthe, Friesland, Groningen)."

Author information

Authors and affiliations.

Department of Endocrinology and Diabetes, Royal Perth Hospital, Perth, WA, 6009, Australia

Kharis Burns

Medical School, University of Western Australia, Nedlands, WA, Australia

Kharis Burns & Bronwyn G. A. Stuckey

Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, Australia

Benjamin H. Mullin, Scott G. Wilson & Bronwyn G. A. Stuckey

School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia

Benjamin H. Mullin & Scott G. Wilson

Department of Internal Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands

Loes M. E. Moolhuijsen & Jenny A. Visser

Estonian Genome Center, Institute of Genomics, University of Tartu, Tartu, Estonia

Triin Laisk & Reedik Mägi

Center for Child, Adolescent and Maternal Health Research, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland

Jaakko S. Tyrmi & Hannele Laivuori

Center for Life Course Health Research, Faculty of Medicine, University of Oulu, Oulu, Finland

Jaakko S. Tyrmi

Division of Endocrinology, Diabetes, and Metabolism, Cedars-Sinai Medical Center, Los Angeles, CA, USA

Jinrui Cui & Mark O. Goodarzi

Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA

Ky’Era V. Actkins

Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA

Ky’Era V. Actkins & Lea K. Davis

Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN, USA

Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Center, Rotterdam, the Netherlands

Yvonne V. Louwers & Joop S. E. Laven

Population Health Sciences, University of Leicester, Leicester, UK

Frank Dudbridge

Obstetrics & Gynecology, Medicine, and Healthcare Organization & Policy, Schools of Medicine and Public Health, University of Alabama at Birmingham, Birmingham, AL, USA

Ricardo Azziz

Department of Obstetrics and Gynecology, Tampere University Hospital, Tampere, Finland

Hannele Laivuori

Institute for Molecular Medicine Finland, FIMM, hiLIFE, University of Helsinki, Helsinki, Finland

Medical and Clinical Genetics, University of Helsinki and Helsinki University Hospital, Helsinki, Finland

Department of Twin Research and Genetic Epidemiology, King’s College London, London, UK

Scott G. Wilson

MRC Epidemiology Unit, Cambridge Biomedical Campus, University of Cambridge School of Clinical Medicine, Cambridge, UK

  • Felix R. Day

Keogh Institute for Medical Research, Nedlands, WA, Australia

Bronwyn G. A. Stuckey

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Estonian Biobank Research Team

  • Andres Metspalu
  • , Lili Milani
  • , Tõnu Esko
  • , Mari Nelis
  •  & Georgi Hudjashov

International PCOS Consortium

  • , Tugce Karaderi
  • , Michelle R. Jones
  • , Cindy Meun
  • , Chunyan He
  • , Alex Drong
  • , Peter Kraft
  • , Hongyan Huang
  • , Linda Broer
  • , Reedik Mägi
  • , Richa Saxena
  • , Jaakko S. Tyrmi
  • , Triin Laisk
  • , Andres Metspalu
  • , Georgi Hudjashov
  • , Margrit Urbanek
  • , M. Geoffrey Hayes
  • , Gudmar Thorleifsson
  • , Juan Fernandez-Tajes
  • , Anubha Mahajan
  • , Kharis Burns
  • , Benjamin H. Mullin
  • , Bronwyn G. A. Stuckey
  • , Timothy D. Spector
  • , Scott G. Wilson
  • , Frank Dudbridge
  • , Jinrui Cui
  • , Mark O. Goodarzi
  • , Ky’Era V. Actkins
  • , Lea K. Davis
  • , Barbara Obermayer-Pietsch
  • , André G. Uitterlinden
  • , Verneri Anttila
  • , Benjamin M. Neale
  • , Marjo-Riitta Jarvelin
  • , Hannele Laivuori
  • , Mark Daly
  • , Bart Fauser
  • , Irina Kowalska
  • , Loes M. E. Moolhuijsen
  • , Yvonne V. Louwers
  • , Jenny A. Visser
  • , Marianne Andersen
  • , Elisabet Stener-Victorin
  • , David Ehrmann
  • , Richard S. Legro
  • , Andres Salumets
  • , Mark I. McCarthy
  • , Laure Morin-Papunen
  • , Unnur Thorsteinsdottir
  • , Kari Stefansson

The Maziko trial team

  • Unnur Styrkarsdottir
  • , John R. B. Perry
  • , Andrea Dunaif
  • , Joop S. E. Laven
  • , Steve Franks
  • , Cecilia M. Lindgren
  •  & Corrine K. Welt

Contributions

Conceived and designed the study: KAB, BHM, FD, SGW, BGAS. Performed the genotyping and genotype imputation: BHM, LMEM, JST, Finngen, TL, KA, JC, Estonian Biobank Research Team. Performed the phenotyping: KAB, SGW, BGAS, Estonian Biobank Research Team, HL, JST, Finngen. Analysed the data/performed the statistical analysis: BHM, FD, LMEM, TL, RM. Drafted the manuscript: KAB, BHM, FD, SGW. Reviewed and edited the manuscript: HL, JAV, JST, YL, LMEM, LKD, TL, KA, JL, RM, MG, RA, FRD, BGAS. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Kharis Burns .

Ethics declarations

Ethics approval and consent to participate.

All subjects in the study provided written informed consent and the experimental protocols were approved for individual cohorts as follows:

Cedars Sinai -The study was approved by the institutional review boards of the recruiting centers and Cedars-Sinai Medical Center (CSMC). Written informed consent was obtained from all participants. BioVU – Approved by the Institutional Review Board at Vanderbilt University (#160279).

WA-PCOS by the SCGOPHCG Human Research Ethics Committee (RGS0000001467) and controls by HRA North West – Liverpool East Research Ethics Committee (19/NW/0187; TwinsUK).

-Estonian Biobank—All biobank participants have signed a broad informed consent form and analyses were carried out under ethical approval 1.1–12/624 from the Estonian Committee on Bioethics and Human Research (Estonian Ministry of Social Affairs) and data release N05 from the EstBB.

-FinnGen—Patients and control subjects in FinnGen provided informed consent for biobank research, based on the Finnish Biobank Act. Alternatively, separate research cohorts, collected prior the Finnish Biobank Act came into effect (in September 2013) and start of FinnGen (August 2017), were collected based on study-specific consents and later transferred to the Finnish biobanks after approval by Fimea (Finnish Medicines Agency), the National Supervisory Authority for Welfare and Health. Recruitment protocols followed the biobank protocols approved by Fimea. The Coordinating Ethics Committee of the Hospital District of Helsinki and Uusimaa (HUS) statement number for the FinnGen study is Nr HUS/990/2017.

The FinnGen study is approved by Finnish Institute for Health and Welfare (permit numbers: THL/2031/6.02.00/2017, THL/1101/5.05.00/2017, THL/341/6.02.00/2018, THL/2222/6.02.00/2018, THL/283/6.02.00/2019, THL/1721/5.05.00/2019 and THL/1524/5.05.00/2020), Digital and population data service agency (permit numbers: VRK43431/2017–3, VRK/6909/2018–3, VRK/4415/2019–3), the Social Insurance Institution (permit numbers: KELA 58/522/2017, KELA 131/522/2018, KELA 70/522/2019, KELA 98/522/2019, KELA 134/522/2019, KELA 138/522/2019, KELA 2/522/2020, KELA 16/522/2020), Findata permit numbers THL/2364/14.02/2020, THL/4055/14.06.00/2020,,THL/3433/14.06.00/2020, THL/4432/14.06/2020, THL/5189/14.06/2020, THL/5894/14.06.00/2020, THL/6619/14.06.00/2020, THL/209/14.06.00/2021, THL/688/14.06.00/2021, THL/1284/14.06.00/2021, THL/1965/14.06.00/2021, THL/5546/14.02.00/2020 and Statistics Finland (permit numbers: TK-53–1041-17 and TK/143/07.03.00/2020 (earlier TK-53–90-20)).

The Biobank Access Decisions for FinnGen samples and data utilized in FinnGen Data Freeze 7 include: THL Biobank BB2017_55, BB2017_111, BB2018_19, BB_2018_34, BB_2018_67, BB2018_71, BB2019_7, BB2019_8, BB2019_26, BB2020_1, Finnish Red Cross Blood Service Biobank 7.12.2017, Helsinki Biobank HUS/359/2017, Auria Biobank AB17-5154 and amendment #1 (August 17 2020), Biobank Borealis of Northern Finland_2017_1013, Biobank of Eastern Finland 1186/2018 and amendment 22 § /2020, Finnish Clinical Biobank Tampere MH0004 and amendments (21.02.2020 & 06.10.2020), Central Finland Biobank 1–2017, and Terveystalo Biobank STB 2018001.

- Rotterdam—The Rotterdam PCOS cohort, was approved by institutional review board (Medical Ethics Committee) of the Erasmus Medical Center (04–263).

Controls from the Lifelines Cohort Study have been approved by the UMCG Medical ethical committee under number 2007/152.

All methods were carried out in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable.

Competing interests

The FinnGen project is funded by the following industry partners: AbbVie Inc., AstraZeneca UK Ltd, Biogen MA Inc., Bristol Myers Squibb (and Celgene Corporation & Celgene International II Sarl), Genentech Inc., Merck Sharp & Dohme Corp., Pfizer Inc., GlaxoSmithKline Intellectual Property Development Ltd., Sanofi US Services Inc., Maze Therapeutics Inc., Janssen Biotech Inc, Novartis AG, and Boehringer Ingelheim International GmbH. All other authors declare that they have no competing interests.

Additional information

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Supplementary Information

Additional file 1:.

Supplementary Figure 1A . QQ plots for SNP-based analyses for each BMI strata in the meta-analysis of genome-wide association studies for PCOS. A) Lean BMI ≤ 25 kg/m 2 (λ=1.01) B) overweight 25 < BMI < 30 kg/m 2 (λ=1.01) C) obese BMI ≥ 30 kg/m 2 (λ=1.02) D) combined overweight/obese (non-lean) groups (λ=1.01) E) all groups combined (λ=1.04). The lean group demonstrates a greater number of highly significant p -values than the overweight and obese groups, likely due to the comparatively larger sample size. Supplementary Figure 1B . QQ plots for gene-based analyses for each BMI strata in the meta-analysis of genome-wide association studies for PCOS A) Lean BMI ≤ 25 kg/m 2 gene-based analysis, B) overweight 25 < BMI < 30 kg/m 2 gene-based analysis, C) obese BMI ≥ 30 kg/m 2 gene-based analysis D) combined overweight/obese (non-lean) groups (gene-based analysis), E) all groups combined gene-based analysis.

Additional file 2: Supplementary Figure 2

. Manhattan plot displaying the results of the lean PCOS single-variant based meta-analysis. Genome-wide significant loci labelled and the threshold for genome wide significance ( P < 5 x 10 8 ) is shown in red.

Additional file 3:

Supplementary Figure 3 . Miami plot depicting the meta-analysis results for the lean (upper panel) and combined overweight/obese PCOS (lower panel) strata. Genome-wide significant loci are labelled and the thresholds for genome-wide significance ( P < 5 x 10 8 ) and genome-wide suggestive significance ( P < 5 x 10 6 ) are shown in red and orange respectively.

Additional file 4: Supplementary Figure 4

. Manhattan plot displaying the results of the combined overweight/obese PCOS single-variant based meta-analysis. The genome-wide significant locus is labelled and the threshold for genome wide significance ( P < 5 x 10 8 ) is shown in red.

Additional file 5:

Supplementary Figure 5 . Annotation of genome-wide significant signals from meta-analysis of the lean PCOS strata using FUMA software [ 10 ]. Plots show the characteristics of each genome-wide significant locus in terms of the physical size, number of potentially relevant SNPs and genes at each locus.

Additional file 6:

Supplementary Figure 6 . Manhattan plot displaying the results from the lean PCOS gene-based meta-analysis. The genome-wide significant genes are labelled and the threshold for genome wide significance ( P < 1.96 x 10 6 ) is shown in red.

Additional file 7:

Supplementary Figure 7 . Manhattan plot displaying the results from the combined overweight/obese PCOS gene-based meta-analysis with a single genome-wide significant gene labelled. The threshold for genome wide significance ( P < 1.96 x 10 6 ) is shown in red.

Additional file 8: Supplementary Table 1

. Results in each BMI subgroup for loci demonstrating genome-wide suggestive association ( P <5x10 -6 ) with lean PCOS in the individual-variant meta-analysis.

Additional file 9: Supplementary Table 2

. Cohort-specific results for genome-wide significant association signals identified in the lean PCOS meta-analysis.

Additional file 10: Supplementary Table 3

. Loci meeting genome-wide suggestive significance ( P < 5 x 10 -6 ) in the combined overweight/obese strata individual-variant based meta-analysis, with comparative data from the lean stratum.

Additional file 11: Supplementary Table 4

. Summary of loci associated with PCOS from previous GWAS reported in the literature showing the level of significance in this BMI-stratified PCOS meta-analysis.

Additional file 12: Supplementary Table 5

. Descriptive information for the six cohorts included in the meta-analyses.

Additional file 13: Supplementary Table 6

. FinnGen Banner Authors 2023.

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Burns, K., Mullin, B.H., Moolhuijsen, L.M.E. et al. Body mass index stratified meta-analysis of genome-wide association studies of polycystic ovary syndrome in women of European ancestry. BMC Genomics 25 , 208 (2024). https://doi.org/10.1186/s12864-024-09990-w

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  • Association between change in cardiorespiratory fitness and prostate cancer incidence and mortality in 57 652 Swedish men
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  • http://orcid.org/0000-0002-5140-9098 Kate A Bolam 1 ,
  • Emil Bojsen-Møller 1 ,
  • Peter Wallin 2 ,
  • Sofia Paulsson 2 ,
  • Magnus Lindwall 1 , 3 ,
  • http://orcid.org/0000-0002-5617-9076 Helene Rundqvist 4 ,
  • http://orcid.org/0000-0002-3901-7833 Elin Ekblom-Bak 1
  • 1 Department of Physical Activity and Health , Swedish School of Sport and Health Sciences GIH , Stockholm , Sweden
  • 2 Research Department , HPI Health Profile Institute , Stockholm , Sweden
  • 3 Department of Psychology , University of Gothenburg , Goteborg , Sweden
  • 4 Department of Laboratory Medicine , Karolinska Institutet , Stockholm , Sweden
  • Correspondence to Dr Kate A Bolam, Department of Physical Activity and Health, Swedish School of Sport and Health Sciences GIH, Stockholm 114 33, Sweden; kate.bolam{at}gih.se

Objectives To examine the associations between changes in cardiorespiratory fitness (CRF) in adulthood and prostate cancer incidence and mortality.

Methods In this prospective study, men who completed an occupational health profile assessment including at least two valid submaximal CRF tests, performed on a cycle ergometer, were included in the study. Data on prostate cancer incidence and mortality were derived from national registers. HRs and CIs were calculated using Cox proportional hazard regression with inverse probability treatment weights of time-varying covariates.

Results During a mean follow-up time of 6.7 years (SD 4.9), 592 (1%) of the 57 652 men were diagnosed with prostate cancer, and 46 (0.08%) died with prostate cancer as the primary cause of death. An increase in absolute CRF (as % of L/min) was associated with a reduced risk of prostate cancer incidence (HR 0.98, 95% CI 0.96 to 0.99) but not mortality, in the fully adjusted model. When participants were grouped as having increased (+3%), stable (±3%) or decreased (−3%) CRF, those with increased fitness also had a reduced risk of prostate cancer incidence compared with those with decreased fitness (HR 0.65, 95% CI 0.49 to 0.86), in the fully adjusted model.

Conclusion In this study of employed Swedish men, change in CRF was inversely associated with risk of prostate cancer incidence, but not mortality. Change in CRF appears to be important for reducing the risk of prostate cancer.

  • Physical fitness

Data availability statement

Data may be obtained from a third party and are not publicly available. The data underlying the findings in this study are currently not publicly available as the original ethical approval application and the informed consent form did not include such direct, free access to the data. Data are stored by and can be requested from the HPI Health Profile Institute at [email protected].

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/ .

https://doi.org/10.1136/bjsports-2023-107007

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WHAT IS ALREADY KNOWN ON THIS TOPIC

Cardiorespiratory fitness (CRF) is associated with the risk of being diagnosed with, or dying from, certain cancer types.

The associations between CRF measured at one time point and risk of prostate cancer incidence are contradictory, which may be the result of the influence of higher prostate cancer screening rates in men with higher fitness.

WHAT THIS STUDY ADDS

Our results suggest that increases in CRF are inversely associated with risk of prostate cancer incidence, but not mortality.

The results highlight the importance of CRF for prostate cancer risk, which has been challenging to determine with single timepoint studies.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

Improvements in CRF in adult men should be encouraged and may reduce the risk of prostate cancer.

Introduction

Unlike other common cancers such as breast, colon and lung cancer, there are relatively few preventable risk factors with strong evidence for reducing prostate cancer risk. Aside from developmental factors, being diagnosed with overweight or obesity are the main risk factors for developing advanced prostate cancer, but insufficient evidence exists to extend this conclusion to non-advanced prostate cancer. 1

While there are well-established relationships between physical activity levels and the incidence and mortality of an increasing number of cancer types, the evidence for prostate cancer is not conclusive. 2 Several studies have reported a decreased risk of prostate cancer incidence, while others have reported an increased risk of prostate cancer for those with higher physical activity levels. 2 Fewer still have investigated the relationships between cardiorespiratory fitness (CRF) and prostate cancer incidence and mortality risk. Local and systemic inflammation is associated with increased risk of (advanced) prostate cancer; therefore, there is an increasing focus on understanding the role of CRF on cancer risk because of the favourable associations between CRF and systemic inflammation. 3 Additionally, CRF has shown to have desirable associations with abdominal obesity, 4 dyslipidaemia 5 and insulin sensitivity. 6 In the studies that have investigated this relationship between CRF and cancer, the findings generally mirror those conflicting findings in studies of physical activity and cancer risk. 7–11 The tendency for men with higher CRF to also have higher prostate cancer screening participation rates may be an influencing factor to explain these inconsistent findings. 7 10

Examining the association between change in CRF over two time points and prostate cancer incidence and mortality risk could contribute to our understanding of the role of CRF as a risk factor. To date, only four smaller studies have investigated the association between change in CRF or physical activity and cancer incidence or mortality. 12–15 Despite the known differences in mechanisms behind both the development of different cancers and the role CRF may play in reducing the risk of cancer, none of these studies examined either incidence or mortality by specific cancer type. To better understand the relationship between CRF and prostate cancer incidence and mortality, and to contribute to cancer-specific prevention recommendations, it is essential to conduct analyses by cancer type. Therefore, the aim of the current study was to determine if there were any associations between changes in CRF and prostate cancer incidence and mortality.

In this prospective cohort study, data were drawn from the health profile assessment (HPA) database, managed by the HPI Health Profile Institute (HPI, Stockholm Sweden). Participation in the HPA was optional, usually offered to all employees working at an associated company or organisation and conducted by an occupational and health service with no financial cost to the employees. HPI was contracted by the occupational health services and responsible for the development and standardisation of the method, education of data collection staff, and administration of the central database. Each HPA consisted of a questionnaire assessing physical activity, lifestyle, perceived health, measurement of body mass and height, and a submaximal ergometer CRF test.

From October 1982 until December 2019 (month of follow-up of outcome data in national registers) data from a total of 181 673 men (aged 18 years and older) were stored in the central HPA database. People were included if they had data for all covariates included in the full analyses (age, education level, body mass index (BMI) and smoking), and at least two valid CRF tests from two separate health assessments, 11 months or more apart. For participants who had more than two tests, only their first and last tests were included in the analyses. Participants were excluded if they had already been diagnosed with prostate cancer before the second health assessment, and only men were included in the study population.

Assessment of CRF

The standardised Åstrand test, a submaximal cycle ergometer test, was used to assess the study exposure variable CRF as estimated VO 2max . 16–18 Previously, the Åstrand test has been validated against directly measured VO 2max during a maximal treadmill test to exhaustion in an adult population. The validation study demonstrated a marginal and insignificant mean difference of −0.07 L/min (95% CI −0.21 to 0.06) in VO 2max between the Åstrand test and VO 2max measured directly. The SE of estimate was 0.48 L/min and the coefficient of variation was 18.1%, which align with validations of other submaximal VO 2max tests. 16 Participants were requested to refrain from the following before the test: vigorous activity the day before, consuming a heavy meal 3 hours before, smoking/snuff use 1 hour before and avoiding stress directly before test. Change in CRF was expressed as absolute (L/min) and relative (mL/kg/min) per year and divided into groups based on if their absolute CRF increased by more than 3% (increase), decreased by more than 3% (decrease) or remained within ±3% (stable). In addition, we divided participants into tertials according to their baseline relative CRF, resulting in three equally sized groups: low CRF (<32.4 mL/kg/min), moderate CRF (32.4–40.7 mL/kg/min) and high CRF (>40.7 mL/kg/min). In this stratified analysis the individual change in absolute CRF was standardised to the mean and SD of the baseline relative CRF category group the individual belonged to, in order to minimise the regression toward the mean effect of the groups.

Prostate cancer incidence and mortality

The Swedish National Hospital and National Cause of Death registries 19 were used to draw data on prostate cancer diagnosis and mortality. This data was linked to the HPA database by linking each participant’s unique Swedish personal identification number. For the incidence analyses, all participants were followed from the date of the last HPA to the date of their prostate cancer diagnosis, death (of any cause) or until 31 December 2019. For the mortality analyses, all participants were followed from the date of their second HPA to either the date of death from prostate cancer, death from any cause, or until 31 December 2019. The ICD-10 code used to identify prostate cancer was C61.

Assessment of covariates

Covariates were included based on current evidence of their potential to influence the relationship between CRF and prostate cancer incidence or mortality. Highest level of education attained at the time of the HPA (defined as length of education <9 years to postgraduate education) was obtained from Statistics Sweden by linking the participant personal identity number. Smoking at the time of the HPA was self-reported using the following statements: I smoke … with the options: At least 20 cig/day, 11–19 cig/day, 1–10 cig/day, occasionally or never. Body mass was assessed at the HPA with a calibrated scale in light-weight clothing to the nearest 0.5 kg. Height was assessed at the HPA using a wall mounted stadiometer and measured to the nearest 0.5 cm. BMI (kg/m 2 ) was subsequently calculated.

Patient and public involvement

We did not involve patients or the public in the design or while conducting our research. In addition to scientific journal articles, the results of the study will be disseminated to the public through online print media and with the cancer community through the Swedish Cancer Society.

Equity, diversity and inclusion statement

Our study did not purposefully exclude people based on their race, ethnicity or socioeconomic level. Information on race, ethnicity or socioeconomic level was not included in the database. The project group included four women and three men and was led by a woman. Researchers involved are from all career levels from postdoctoral researcher to professor. All researchers reside in Stockholm, Sweden.

Statistical analyses

Outliers that lay −20% and 20% (L/min/year) from the mean were removed (n=1319) to minimise influence of measurement error, as this level of change per year over several years is extremely rare and unlikely. Associations between CRF at baseline and at follow-up and prostate cancer incidence and mortality were analysed using Cox proportional hazard regression models. Associations between changes in CRF and prostate cancer incidence and mortality were analysed using Cox proportional hazard regression models with inverse probability treatment weights of time-varying confounders such as age, BMI and smoking. Non-time varying confounders (education, baseline CRF and year of last HPA test) were adjusted for conventionally. For visualisation purposes, restricted cubic splines with knots at 5th, 50th and 95th percentile were performed for % change in absolute CRF with 0% change as the reference.

Four models were created with an increasing number of variables for each model. Model 1 included only baseline CRF. Model 2 additionally included age, education and year of the last HPA test. Model 3 additionally included BMI, and model 4 further included smoking. Model 5 ( online supplemental file ) additionally included adjustment for self-reported physical activity. Baseline CRF was not adjusted for in the one timepoint analysis (baseline and follow-up associations) or in the subanalysis stratified by baseline CRF.

Supplemental material

In the subgroup analyses, Cox proportional hazard modelling with inverse probability treatment weight of time-varying confounders was used to examine the relationships between the groups, stratified by direction of change in absolute fitness (stable, decrease and increase) and baseline relative CRF (low, moderate and high), and prostate cancer incidence and mortality. For all models the proportional hazard assumption was checked using scaled Schoenfeld residuals. To investigate if change in absolute CRF were associated with change in self-reported physical activity, a linear regression weighted for age, and adjusted for education, and the year of the last HPA test was performed.

Sensitivity analysis to address potential reverse causality was performed by dropping incident cases that occurred ≤2 years after the last HPA test for the main analysis and the grouped (increase, decrease and stable) analysis.

All statistical analyses were performed using R Studio, V.4.2.1 (2022-06-23). 20 The IPW package 21 was used to create inverse probability treatment weights and the survival 22 package was used to create Cox proportional hazard regression models. The splines, 20 ggplot2 23 and survminer 24 package were used to visualise the restricted cubic splines. Conduct and presentation of statistical analyses in this study are in accordance with the CHecklist for statistical Assessment of Medical Papers) statement. 25

Among the 181 673 men, 58 971 met the criteria of having undertaken a minimum of two tests spaced at least 11 months apart. We excluded 1319 individuals due to a CRF decrease or increase of over 20% per year ( figure 1 ). The analytic sample consisted of 57 652 men, with a mean age of 41.4 years (range 18–79 years) and an average BMI of 26.0 kg/m 2 (SD 3.6) at the first HPA ( table 1 ). Of the 57 652 men, 592 (1%) were diagnosed with prostate cancer, while 46 (0.08%) died of prostate cancer as the primary cause of death. At baseline, the sample’s mean relative and absolute CRF were 37.4 mL/kg/min and 3.12 L/min, respectively. From the first to the second HPA relative CRF decreased by 0.27 mL/kg/min (SD 2.2), while absolute CRF decreased by 0.01 L/min (SD 0.17), on average. The time between the tests was on average 4.9 years (SD 3.6). The mean follow-up time for the incidence analyses was 6.7 years (SD 4.9) from the last HPA test.

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Flow chart of participant inclusion.

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Participant descriptive characteristics, all, and grouped by changes in and baseline cardiorespiratory fitness

There was no association between baseline CRF or CRF at last test and the risk of prostate cancer incidence, when the models were adjusted for relevant covariates ( online supplemental table s1 ). Only in the unadjusted model 1 was there an inverse association between CRF both at baseline and at last test and the risk of incidence prostate cancer.

Percentage change in absolute CRF (L/min) was inversely associated with risk of being diagnosed with prostate cancer ( figure 2 and table 2 ) and remained significant after adjusting for all covariates (baseline CRF, age, education level, year of test, BMI, smoking) ( table 2 ) and physical activity ( online supplemental table s2 ). In comparison, per cent change in relative CRF (mL/kg/min) was associated with prostate cancer incidence only for model 1 (adjusted for baseline CRF).

Restricted cubic splines of the Cox proportional model examining the association between % change in cardiorespiratory fitness and incidence of prostate cancer. Model 1: adjusted for baseline fitness. Model 2: adjusted for baseline fitness, age, education and year of last test. Model 3: adjusted for baseline fitness, age, education, year of last test and body mass index. Model 4: adjusted for baseline fitness, age, education, year of last test, body mass index and smoking. BMI, body mass index; VO 2max , estimated maximal oxygen consumption.

HRs with 95% CIs for the association between change in cardiorespiratory fitness and prostate cancer incidence and mortality

When participants were grouped by those with increased (+3%), stable (±3%) or decreased (−3%) absolute CRF, those with increased CRF had significantly lower cancer incidence risk compared with those who held their CRF stable ( figure 3 ). The associations remained significant after adjusting for the covariates in all models. In a sensitivity analysis, individuals who were diagnosed with prostate cancer in the 2 years following the last HPA were excluded (n=103). The sensitivity analyses showed that the association between absolute CRF and prostate cancer risk remained significant (see online supplemental table s3 ). However, in the directional analysis, comparing the stable group to the decreased and increased group, models 2 and 3 were no longer significant.

Cox proportional HRs with 95% CIs showing decrease (−3%) compared with stable (±3%) and increase (+3%). Model 1: adjusted for baseline fitness. Model 2: adjusted for baseline fitness, age, education and year of last test. Model 3: adjusted for baseline fitness, age, education, year of last test and body mass index. Model 4: adjusted for baseline fitness, age, education, year of last test, body mass index and smoking. *p<0.05; **p<0.01; ***p<0.001.

Figure 4 shows the results from subgroup analyses stratified by baseline relative CRF using group-standardised absolute fitness change. For the group with moderate baseline CRF (32.4–40.7 mL/kg/min), every SD increase in absolute CRF (L/min) reduced the risk of prostate cancer incidence by 16% for model 1. Significant associations remained even after adjusting for covariates in models 2 to 4. None of the models yielded significant associations for the low and high fitness groups. Even when using the percentage change in absolute fitness to analyse the data, the results remained consistent with the standardised analysis. However, in the case of the high fitness group, the least adjusted model (model 1) did show a significant inverse association with prostate cancer incidence, but this association was attenuated when adjusting for covariates (see online supplemental table s4 ).

Cox proportional HRs with 95% CIs for the association between change in cardiorespiratory fitness and incidence of prostate cancer within low, moderate and high baseline cardiorespiratory fitness groups. Model 1: adjusted for baseline fitness. Model 2: adjusted for baseline fitness, age, education and year of last test. Model 3: adjusted for baseline fitness, age, education, year of last test, and body mass index. Model 4: adjusted for baseline fitness, age, education, year of last test, body mass index and smoking. *p<0.05; **p<0.01; ***p<0.001.

Change in absolute CRF was positively associated with changes in self-reported physical activity (see online supplemental table s5 ). Only 46 prostate cancer deaths were observed and changes in CRF were not associated with prostate cancer mortality ( table 2 ).

This is the largest study to examine the relationships between change in CRF and cancer incidence and mortality, and the first study to examine change in CRF specifically on prostate cancer incidence and mortality. The main finding of this study of over 57 000 men were that change in CRF (% L/min) was inversely associated with the risk of prostate cancer incidence and remained significant despite adjusting for relevant covariates. Subsequently, individuals with an annual increase in absolute CRF by 3% or more had a significantly lower risk of being diagnosed with cancer compared with individuals whose CRF was stable. When the participants were grouped by baseline CRF, the association between change in absolute CRF and prostate cancer incidence was only significant for the group with moderate baseline CRF. Changes in both absolute and relative CRF were not associated with prostate cancer mortality.

The findings in the present study contribute significantly to our knowledge of the relationship between CRF and prostate cancer as it is the first study to investigate change in CRF rather than CRF at a single time point, and to focus on prostate cancer specifically. Contrary to other cancer types, in the studies that have examined the relationship between CRF at one time point and prostate cancer incidence, the majority have reported an increased risk of prostate cancer incidence with increasing CRF, however there are studies that have reported the opposite. 2 7–10 While the reason for these positive associations may not be due to a ‘true’ increased risk for those with higher CRF, but in part due to the influence of higher prostate cancer screening rates in men with higher CRF. This cannot be confirmed in the current analyses due to lack of information on screening rates. 2

Analyses showed a reduced risk for prostate cancer incidence for those who increased their absolute CRF by more than 3%. In context, meta-analyses in adults have shown a person’s CRF can be improved by up to 16% in exercise interventions shorter than 1 year in duration. 26 27 In the only other study to investigate change in CRF and cancer incidence, Robsahm et al 14 reported similar findings to the current study, that in comparison to a decrease in CRF (>5%), an increase in CRF (>5%) was associated with 19% lower cancer incidence. 14

When the full group was stratified by baseline CRF, a reduced risk for prostate cancer incidence (−15%) was seen only in those with moderate CRF. While we can only speculate on the reason for this, it may be that improving one’s CRF from an already high baseline does not confer any discernible additional benefits. It may also be that the increases in CRF in people with low CRF were not sufficient to reach a potential threshold needed to contribute to lowering their risk of prostate cancer. In addition, residual confounding may account for the lack of associations. There is a possibility that the observed change in both the high and low groups may, in part, be a result of a regression to the mean. This means that individuals with initially extreme values, whether high or low, are more likely to have less extreme values on subsequent tests, due to random variation, rather than a change in their underlying fitness level. Consequently, it is plausible to suggest that only individuals in the moderate fitness group have the potential to show changes in both directions. This group’s fitness level may change, in a manner that is more reflective of actual change in their fitness, without the influence of regression to the mean.

Change in CRF was not associated with prostate cancer mortality in the current study. While no study has investigated the association between change in CRF and prostate cancer mortality, three studies have investigated the associations between CRF and cancer mortality in general. 13–15 These studies in men found that higher CRF was associated with a 16%–30% lower risk of cancer mortality. Only 46 prostate cancer-related deaths were observed in the present study, and therefore the analyses may not have been sufficiently powered to detect any associations. There is also considerable competing mortality risk from other chronic diseases, such as cardiovascular and metabolic disease, associated with prostate cancer treatment side effects. 28 It would therefore be of interest to examine the associations between CRF and mortality from these diseases in men diagnosed with prostate cancer.

The strengths of this study are the large sample size, the possibility to adjust for relevant covariates and the access to the national registry. Importantly, the study focused on a specific cancer type ensuring prostate specific conclusions. A novelty of the study was the objective measurement of CRF at two timepoints using standardised methodology.

Clinical implications

Where previous cancer prevention recommendations have focused on physical activity, the findings of this study provide further clarity on the associations between CRF and cancer incidence in an area of research with conflicting results. Although highly complex in nature, these investigations that aim to understand potential mechanisms behind the beneficial role of physical activity for preventing cancer will lead to more targeted prevention recommendations. The results of this study highlight the important role of supporting the general public to increase their CRF or aim to reach moderate fitness levels.

Limitations

While measuring VO 2max directly during a maximal protocol with spirometry is the gold standard, it was not possible in this study. The submaximal protocol used in this study has however been reported to produce valid and reliable estimations compared with directly measured VO 2max . 16 Furthermore, the submaximal test used has not been validated in change studies, and this must be taken into consideration when translating the findings from this study. It is also important to note that there is a significant genetic component to both an individual’s CRF levels and cancer risk, which must be considered when interpreting the results. Furthermore, the recruited group were employed and therefore findings may not be generalisable to populations outside of this demographic, particularly people who are unemployed. Unfortunately, information on race or ethnicity was not recorded in the current data set, therefore it was not possible to conduct analyses among the different groups. In the present study, two time points were used to capture changes in CRF. It has been put forward that at least three time points are needed to establish the true trajectory of change. 29 However, as relatively few individuals in the current study had data for three or more time points, we decided to include those with at least two time points. Finally, while there is an established link between systemic inflammation and advanced prostate cancer, the mechanism between less aggressive or localised prostate tumours is not fully understood and warrants future research.

Conclusions

In this large study of Swedish men, change in CRF was inversely associated with risk of prostate cancer incidence, but not prostate cancer mortality. Participants whose CRF increased by more than 3% had a significantly lower risk of prostate cancer incidence.

Ethics statements

Patient consent for publication.

Not applicable.

Ethics approval

The study was approved by the Stockholm Ethics Review Board (Dnr 2015/1864-31/2, 2016/9-32 and 2019-05711), and adhered to the Declaration of Helsinki.

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Supplementary materials

Supplementary data.

This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

  • Data supplement 1

KAB and EB-M are joint first authors.

Twitter @katebolam

Contributors All authors have contributed with the conception and design of the work. KAB and EB-M contributed equally to this paper and share joint first authorship. SP contributed to the acquisition of the data. EB-M contributed by conducting the analyses and he and KAB interpreted the data. KAB and EB-M drafted the work, while all authors have revised the work and contributed with intellectual content. EE-B and EB-M monitored adherence to the design and statistical analyses. All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analyses. All authors have approved the final version of the paper to be published and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work were appropriately investigated and resolved. E-EB was responsible for the overall content of the paper as the guarantor.

Funding This study was funded by the Swedish Cancer Society, ref. 21 1837 Pj.

Competing interests None declared.

Patient and public involvement We did not involve patients or the public in the design or while conducting our research. In addition to scientific journal articles, the results of the study will be disseminated to the public through online print media and with the cancer community through the Swedish Cancer Society.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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Supreme Court case is about more than regulating social media. Can you comment? Maybe not.

Florida, texas laws on content moderation mean that they won’t just impact social media but also review sites, comment sections on articles and even online listings..

If you read or post in the comments sections accompanying your online news , the U.S. Supreme Court may soon give you a lot to comment about but fewer places to do it. The same diminishing access may apply if you debate with friends and family on Facebook, enjoy sharing memes on X (formerly known as Twitter), leave reviews on Yelp or even list products for sale on Etsy.

A lot of the everyday online platforms that many of us use to connect with friends and family, gain information or run a business provide a place to create user-generated content . As a result, most platforms require some degree of content moderation around what is or isn’t allowed. But state laws in Texas and Florida could change how platforms can handle such content, making them less likely to offer such opportunities for expression to users, which would impact far more than just social media.

The good news for those who enjoy all the opportunities user-generated content creates is the Supreme Court is considering challenges to these laws and the possibility that they violate the First Amendment. The Supreme Court on Monday held oral arguments in the cases of NetChoice v. Paxton and Moody v. NetChoice, each of which tests the constitutionality of the two states’ social media laws.

The law in Texas prohibits social media platforms with more than 50 million active U.S. users from censoring "a user, a user's expression, or a user's ability to receive the expression of another person" and would prevent online services from engaging in content moderation except in a few specific instances.

Florida seeks to limit large social media platforms with “ annual gross revenues in excess of $100 million ” and “at least 100 million monthly individual platform participants globally” from willfully de-platforming a political candidate. Along with other provisions on public contracts, the law aims to categorize big social media platforms as “common carriers.”

Similar social media laws, different legal conclusions

These cases arrived at the Supreme Court after lower courts came to different conclusions on the constitutionality of the two similar laws.

In Moody v. NetChoice , the 11th Circuit ruled that Florida’s provisions on content moderation and disclosure requirements limit platforms’ ability to exercise editorial judgment, therefore triggering First Amendment scrutiny.

Meanwhile, in NetChoice v. Paxton , the 5th Circuit ruled that large social media platforms do not have a First Amendment right to “censor” speech, finding a sufficient state interest to regulate the platforms' conduct.

Posting ‘Zionists must die’ is awful. But it shouldn't get student kicked out of college.

Now, the Supreme Court is considering the underlying question: Do the content moderation restrictions and transparency requirements placed by the Texas and Florida laws each violate the First Amendment rights of the large social media platforms these laws seek to regulate?

Though a great deal of emphasis will be placed on the platform’s First Amendment rights, those rights will also impact the user experience.

It may be easy to think that requiring platforms to permit certain users or content would help ensure that free speech continues to flourish, or that minority viewpoints are not crowded out, but these proposals would create new concerns not only for platforms but also for users.

For example, under the Texas law, a platform serving the Jewish community that fits the law's provisions would not be able to remove lawful but awful antisemitic content. Under the Florida law, anyone could register to run for, say, local dogcatcher and proceed to share videos of animal cruelty and platforms would be unable to respond. 

What about a LinkedIn job fair? Or views on Etsy or Uber?

The Supreme Court hearing raised important questions Monday about what these laws would mean not only for traditional social media but also a LinkedIn virtual job fair, or if Etsy wanted to limit discussion of politics on its platforms.

As Justice Sonia Sotomayor noted to Florida's solicitor general, “It seems like your law is covering just about every social media platform on the internet.”

The ways these laws apply to the content moderation needed for user-generated content means that they won’t just impact social media but also things like review sites, comment sections on articles and even online listings. As the Supreme Court noted, while the Texas law is a bit narrower , the Florida law could impact even platforms like Uber.

Whatever happened to parents’ rights? 'Free state of Florida' wants to ban kids from social media

Some platforms might just choose not to carry user-generated content anymore, given the risk. Others might eliminate the opportunity to discuss certain topics or offer certain products that are perceived as having a viewpoint (although the internet often illustrates that almost anything can become a vehemently held belief and viewpoint).

While the Texas law is narrower on what platforms it covers, it remains very vague on what constitutes a viewpoint in a way that could eliminate any number of both serious and more fanciful internet debates on everything from the upcoming election to Taylor Swift’s impact on the NFL.

While some will try to make the NetChoice cases only about “Big Tech” or social media, the reality is that the Supreme Court’s decision will impact not just the companies but also everyday internet users.

Jennifer Huddleston is a technology policy research fellow at the Cato Institute and an adjunct professor at George Mason University’s Antonin Scalia Law School.

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  1. How to write the conclusion of your case study

    UX case studies must be kept short, and, when considering the length of your beginning, process and conclusion sections, it's the beginning and the conclusion sections that should be the shortest of all. In some case studies, you can keep the ending to two or three short phrases. Other, longer case studies about more complex projects may ...

  2. How to Write Effective Case Study Conclusions

    Your conclusion is an opportunity for you to summarize your findings and highlight what this study has taught you. It should also summarize and draw out the main points you've discussed and reinforce the importance of your work. Remember, your last impression needs to be just as good as your first.

  3. Writing a Research Paper Conclusion

    Step 1: Restate the problem The first task of your conclusion is to remind the reader of your research problem. You will have discussed this problem in depth throughout the body, but now the point is to zoom back out from the details to the bigger picture.

  4. Writing a Case Study

    A case study research paper examines a person, place, event, condition, phenomenon, or other type of subject of analysis in order to extrapolate key themes and results that help predict future trends, illuminate previously hidden issues that can be applied to practice, and/or provide a means for understanding an important research problem with g...

  5. How to Conclude a Case Study

    Knowing how to successfully conclude a case study is one of the most important parts of every case interview. A strong conclusion shows how well you summarize the entire case solution into a couple of points. In addition, it proves that you can successfully back up your arguments with both quantitative and qualitative facts.

  6. Writing a Case Analysis Paper

    Case analysis is a problem-based teaching and learning method that involves critically analyzing complex scenarios within an organizational setting for the purpose of placing the student in a "real world" situation and applying reflection and critical thinking skills to contemplate appropriate solutions, decisions, or recommended courses of action.

  7. How to Write a Thesis or Dissertation Conclusion

    Step 1: Answer your research question Step 2: Summarize and reflect on your research Step 3: Make future recommendations Step 4: Emphasize your contributions to your field Step 5: Wrap up your thesis or dissertation Full conclusion example Conclusion checklist Other interesting articles Frequently asked questions about conclusion sections

  8. 9. The Conclusion

    The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of the main topics covered or a re-statement of your research problem, but a synthesis of key points and, if applicable, where you recommend new areas for future research.

  9. What Is a Case Study?

    Step 1: Select a case Step 2: Build a theoretical framework Step 3: Collect your data Step 4: Describe and analyze the case Other interesting articles When to do a case study A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject.

  10. How to Write the Perfect Conclusion to Your UX Case Study

    2. Demonstrate the Impacts of Your Project. Results are a must-have in your case study's conclusion. Recruiters hire you to bring value to their organization, so they want to see the impact your work has generated. Show results that are linked to the problem statement you introduced at the beginning of your case study.

  11. Develop a conclusion

    In case you haven't caught on, structure is highly important to your success in the case study interview, even in your conclusion, you need to be crystal clear and almost formulaic in your response.

  12. Conclusions

    Conclusions One of the most common questions we receive at the Writing Center is "what am I supposed to do in my conclusion?" This is a difficult question to answer because there's no one right answer to what belongs in a conclusion. How you conclude your paper will depend on where you started—and where you traveled.

  13. Conclusions

    Your conclusion is your chance to have the last word on the subject. The conclusion allows you to have the final say on the issues you have raised in your paper, to synthesize your thoughts, to demonstrate the importance of your ideas, and to propel your reader to a new view of the subject.

  14. How to Write a Case Study: from Outline to Examples

    Conclusion. To conclude, a case study is one of the best methods of getting an overview of what happened to a person, a group, or a situation in practice. It allows you to have an in-depth glance at the real-life problems that businesses, healthcare industry, criminal justice, etc. may face. This insight helps us look at such situations in a ...

  15. How to Write Discussions and Conclusions

    Begin with a clear statement of the principal findings. This will reinforce the main take-away for the reader and set up the rest of the discussion. Explain why the outcomes of your study are important to the reader. Discuss the implications of your findings realistically based on previous literature, highlighting both the strengths and ...

  16. How to Write a Conclusion for Research Papers (with Examples)

    The research paper conclusion serves the following purposes: 1 Warn readers of the possible consequences of not attending to the problem. Recommend specific course (s) of action. Restate key ideas to drive home the ultimate point of your research paper. Provide a "take-home" message that you want the readers to remember about your study.

  17. 22 Writing the conclusion & recommendations

    22 Writing the conclusion & recommendations General. There are probably some overlaps between the Conclusion and the Discussion section. Nevertheless, this section gives you the opportunity to highlight the most important points in your report, and is sometimes the only section read. ... Implications of the study: Place the study in a wider ...

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    Updated February 4, 2021 Image Credits Some might argue that a conclusion is one of the most important components of any research paper or article. It's your last opportunity to make a good impression on your reader.

  19. How to Write a Case Study (+10 Examples & Free Template!)

    Most resources tell you that a case study should be 500-1500 words. We also encourage you to have a prominent snapshot section of 100 words or less. The results and benefits section should take the bulk of the word count. Don't use more words than you need. Let your data, images, and customers quotes do the talking.

  20. Case Study

    Draw conclusions: The conclusions drawn from the case study should be based on the data analysis and should be relevant to the research questions. The conclusions should be supported by evidence and should be clearly stated. ... Subjectivity: Case studies rely on the interpretation of the researcher, which can introduce subjectivity into the ...

  21. Best Case Study Conclusion Guidelines For Students

    The conclusion of the case study is an ignored portion. Several students make case study research papers every year on the demand of their tutors. But, very few of them realize the importance of every segment of it. From the introduction to the case study conclusion, every single thing matters.

  22. Case Study: Definition, Examples, Types, and How to Write

    A case study is an in-depth study of one person, group, or event. In a case study, nearly every aspect of the subject's life and history is analyzed to seek patterns and causes of behavior. Case studies can be used in many different fields, including psychology, medicine, education, anthropology, political science, and social work.

  23. How to Conclude an Essay

    Step 1: Return to your thesis. To begin your conclusion, signal that the essay is coming to an end by returning to your overall argument. Don't just repeat your thesis statement—instead, try to rephrase your argument in a way that shows how it has been developed since the introduction.. Example: Returning to the thesis Braille paved the way for dramatic cultural changes in the way blind ...

  24. E-waste management in Nepal: A case study overcoming challenges and

    Limitations and motivation. This work is entirely derived using the various literary articles and information available in the public domain. The majority of relevant literature on the issue that supports the review's purpose is studied, and a conclusion is formed based on that analysis, which shines a light on the larger concept of this study, which is to uncover the methods of solving these ...

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  29. Association between change in cardiorespiratory fitness and prostate

    The strengths of this study are the large sample size, the possibility to adjust for relevant covariates and the access to the national registry. Importantly, the study focused on a specific cancer type ensuring prostate specific conclusions. A novelty of the study was the objective measurement of CRF at two timepoints using standardised ...

  30. Supreme Court case is about more than regulating social media. Can you

    Similar social media laws, different legal conclusions. These cases arrived at the Supreme Court after lower courts came to different conclusions on the constitutionality of the two similar laws.