Bridging the Gender Gap in Medical Research: Still a Long Way to Go

What is the gender gap in medical research?

Despite growing awareness of the need for equal representation of women in clinical trials, gender imbalances continue to exist.

A study from 2018 analyzing multinational FDA-approved clinical trials found that women represented only 29%–34% of participants in Phase I, 41%–51% in Phase II, and 38%–49% in Phase III.¹Chen A, Wright H, Itana H, Elahi M, Igun A, Soon G, Pariser AR, Fadiran EO. Representation of Women and Minorities in Clinical Trials for New Molecular Entities and Original Therapeutic Biologics Approved by FDA CDER from 2013 to 2015. J Womens Health (Larchmt). 2018 Apr;27(4):418-429. For instance, 61% of patients with psychiatric disorders are women, yet only 42% are represented in related clinical trials. Similar to this, women make up 51% of cancer patients, but only 41% of the participants were women in corresponding clinical trials.²Sosinsky AZ, Rich-Edwards JW, Wiley A, Wright K, Spagnolo PA, Joffe H. Enrollment of female participants in United States drug and device phase 1-3 clinical trials between 2016 and 2019. Contemp Clin Trials. 2022 Apr;115:106718. This shows that, especially in early trial phases, where the safety profile of novel drugs is assessed, women representation is not balanced and  potential differences in treatment responses are underestimated.

Gender disparity in medical research: Where does it stem from and why should we care?

Why the focus on men in clinical trials?

The overrepresentation of men in clinical trials is driven by various factors, including historical repercussions, lack of awareness and socio-cultural biases.

1. Widespread fear due to the Thalidomide scandal in 1962

In 1962, the Thalidomide scandal occurred, in which thalidomide was prescribed to pregnant women to alleviate morning sickness, ultimately causing more than 10,000 severe birth defects.³https://www.sciencemuseum.org.uk/objects-and-stories/medicine/thalidomide This medical disaster had severe consequences on the regulatory framework of clinical trials, leading to a FDA policy in 1977 that recommended the exclusion of women at a child-bearing age for early phases in clinical trials.⁴Kantor, E. (s. d.). Women and clinical trials : The importance of inclusion in research studies. Antidote. https://www.antidote.me/blog/women-and-clinical-trials-the-importance-of-inclusion-in-research-studies It was only in 1993 that the FDA released a guideline encouraging the participation of women in Phase I and II drug trials. However, the effects of this delay are still seen today, resulting in lower enrollment rates of women.

2. Limited awareness of the clinical impact of female-specific physiology

It is often overlooked that the female body functions fundamentally differently than the male body. Women undergo different hormonal cycles, metabolic rates, immune responses and have distinct fat distribution.⁵Singh, K., & Swarup, R. (2025). Women are poorly represented in clinical trials. That’s problematic. Nature. https://doi.org/10.1038/d44151-025-00036-y These differences were long considered to complicate clinical trial data analysis. However, it has since been shown that the physiological differences of women significantly impact pharmacokinetic dynamics, including how a drug is distributed, metabolized and excreted, making safety and efficacy tests critical in both men and women.

3. Socio-cultural gender biases affect female participation in clinical trials

There are various factors that can influence the willingness to participate in clinical trials, including concerns about the risk of side effects, the time required for participation and transportation and the incompatibility with the work schedule.⁶Goldstein, K. M., Kung, L. C. Y., Dailey, S. A., Kroll-Desrosiers, A., Burke, C., Shepherd-Banigan, M., Lumsden, R., Sims, C., Schexnayder, J., Patel, D., Cantrell, S., Sheahan, K. L., & Gierisch, J. M. (2024b). Strategies for enhancing the representation of women in clinical trials : an evidence map. Systematic Reviews, 13(1). https://doi.org/10.1186/s13643-023-02408-w Such challenges often affect more women, as they are still primarily in charge of caregiving responsibilities. In addition, social expectations from family, partners, and friends regarding the role of women in family obligations influence the decision of women on whether or not to participate in clinical trials.⁷Lobato L, Bethony JM, Pereira FB, Grahek SL, Diemert D, Gazzinelli MF. Impact of gender on the decision to participate in a clinical trial: a cross-sectional study. BMC Public Health. 2014 Nov 6;14:1156. Moreover, external concerns about the safety of medication on reproductive health, as well as its effects on pregnancy and breastfeeding, are more pronounced for women.⁸Women in Clinical Trials : Relevance and Differences. (s. d.). https://www.alcedis.de/en/blog/women-clinical-trials-relevance-challenges-and-future-developments

The impact of gender gap in medical research on women’s health

The underrepresentation of women in clinical trials over time results in healthcare disparities in terms of treatment safety and outcomes. Medical neglect of gender differences regarding disease symptoms and treatment response contributes to higher misdiagnosis rates in women. For example, 50% of heart attacks in women are misdiagnosed, resulting in a 70% higher risk of death within 30 days.⁹Wu J, Gale CP, Hall M, et al. Editor’s Choice – Impact of initial hospital diagnosis on mortality for acute myocardial infarction: A national cohort study. European Heart Journal. 2016;7(2):139-148. Moreover, it has been shown that, for marketed therapeutic solutions, women experience 50-75% more adverse drug reactions compared to men, resulting in many drugs being withdrawn from the market due to health risks in women.¹⁰Rademaker M. Do women have more adverse drug reactions? Am J Clin Dermatol. 2001;2(6):349-51.

To highlight the importance of considering gender differences in clinical trials, numerous examples exist where the efficacy of therapeutic solutions, such as medical devices and treatments, revealed major differences between men and women once they were launched. For instance, a study from 2013 showed that women with metal hip replacements were 29% more likely to suffer from implant failure compared to men.¹¹Inacio MCS, Ake CF, Paxton EW, et al. Sex and Risk of Hip Implant Failure: Assessing Total Hip Arthroplasty Outcomes in the United States. JAMA Intern Med. 2013;173(6):435–441. This is likely due to anatomical differences and the insufficient clinical testing in women, which leads to these outcomes.

Another example involves the insomnia drug Zolpidem, which, years after approval, was found to potentially cause more next-morning car accidents in women than in men. This was due to neglecting the need for sex-specific medication dosages, which led to plasma drug concentrations in women twice as high as in men.¹²Michaloski C. B., Katz R. (2011, July 14). Complete Response Letter, NDA #22328 [Letter to Transcept Pharmaceuticals, Inc]. https://www.accessdata.fda.gov/drugsatfda_docs/nda/2011/022328Orig1s000OtherActionLtrs.pdf¹³Michaloski C. B., Katz R. (2011, July 14). Complete Response Letter, NDA #22328 [Letter to Transcept Pharmaceuticals, Inc]. https://www.accessdata.fda.gov/drugsatfda_docs/nda/2011/022328Orig1s000OtherActionLtrs.pdf

Lastly, the drug Digoxin was shown to effectively increase the force of cardiac contractions. However, these results were based on trials with 80% male participants. Years later, when data were analyzed by gender, it was found that women taking Digoxin died earlier than those on a placebo.¹⁴Rathore, S.S.; Wang, Y.; Krumholz, H.M. Sex-Based Differences in the Effect of Digoxin for the Treatment of Heart Failure. N. Engl. J. Med. 2002, 347, 1403–1411.

These examples show that neglecting the female physiology, metabolism and hormonal differences endangers the health of women and compromises treatment effectiveness. Recognizing and tackling gender differences is critical and must be central to clinical research practices.

Discover how our team can support you in your projects related to women’s health >

What is needed to bridge the gender gap in medical research?

Promising steps have already been taken to reduce sex inequalities in medical research

In 2025 the FDA released updated guidelines to reduce the underrepresentation of women in clinical trials for drugs and medical devices in various therapeutic areas. These aim to increase enrollment of females in clinical trials, to analyze and interpret sex-specific data and to include sex-specific information in regulatory submission of medical products.¹⁵FDA issues draft guidance : Study of sex Differences in the clinical evaluation of medical products. (s. d.). https://www.clinicalleader.com/doc/fda-issues-draft-guidance-study-of-sex-differences-in-the-clinical-evaluation-of-medical-products-0001

One of the initiatives the European Union is taking to improve patient representativeness and inclusion in clinical trials, is the READI (Research in Europe and Diversity Inclusion) project, launched in January 2025 under Horizon Europe. This initiative aims to overcome barriers to clinical study participation among underserved and underrepresented communities. It addresses issues such as lack of information, mistrust, poor communication, geographic limitations and prejudice, while emphasizing the importance of integrating gender-based analysis in research and innovation.¹⁶READI Project Launches to Enhance Patient Representativeness and Inclusion in European Clinical Research. (s. d.). Ecrin. https://ecrin.org/news/readi-project-launches-enhance-patient-representativeness-and-inclusion-european-clinical¹⁷Gender equality in research and innovation. (s. d.). Research And Innovation. https://research-and-innovation.ec.europa.eu/strategy/strategy-research-and-innovation/democracy-and-rights/gender-equality-research-and-innovation

These recent developments highlight the importance of sex-based differences in drug safety and efficacy, protecting women’s health and raising awareness in both institutions and the public.

There are still opportunities for future progress

Much progress has been made so far, but there are many opportunities for further action to drive meaningful progress, including:

• Promoting gender equality and awareness in research leadership positions: it has been shown that biomedical leadership positions, including clinical investigator roles, are mostly held by men. For instance, only 18% of the cardiovascular clinical trials were led by women. However, it has been shown that clinical trials led by women registered a higher number of female participants.¹⁸Balch, B. (2024, 26 mars). Why we know so little about women’s health. AAMC. https://www.aamc.org/news/why-we-know-so-little-about-women-s-health This underscores the importance of having women in decision-making leadership positions in research, as this drives gender equality and inclusivity in clinical trials.
• Enhancing gender-specific analysis within trials: novel technologies using AI approaches, such as machine learning, hold potential to facilitate sex-specific data analyses to identify gender-related trends and assist physicians in generating an initial diagnosis and predicting treatment outcomes. ¹⁹Joshi, A. (2024). Big data and AI for gender equality in health : bias is a big challenge. Frontiers In Big Data, 7. https://doi.org/10.3389/fdata.2024.1436019 ²⁰Joshi A. Big data and AI for gender equality in health: bias is a big challenge. Front Big Data. 2024 Oct 16;7:1436019. ²¹Chandak P, Tatonetti NP. Using Machine Learning to Identify Adverse Drug Effects Posing Increased Risk to Women. Patterns (N Y). 2020 Oct 9;1(7):100108. Tempus AI is an example of a clinical software provider that uses AI to process clinical data, to develop treatment plans and predict adverse events.²²Healthcare technology provider Tempus AI raises $ 410M in IPO. (2024, 15 juin). SiliconANGLE. https://siliconangle.com/2024/06/14/healthcare-technology-provider-tempus-ai-raises-410m-ipo/ These approaches have a great potential for the future and could be further optimized and tested in clinical trial set-ups.
• Creating a clinical trial framework compatible for women: lastly, it is important to optimize both the recruitment and adherence of women in clinical trials by encouraging and supporting their participation. This includes, among other things, overcoming social and cultural biases, providing sufficient informational material outlining the study plan and potential side effects and addressing logistical barriers. This involves providing childcare and eldercare, transportation and offering flexible participation options, such as treatment at home or at nearby centers, with schedules that adapt to the availability of participants.²³Bierer BE, Meloney LG, Ahmed HR, White SA. Advancing the inclusion of underrepresented women in clinical research. Cell Rep Med. 2022 Mar 7;3(4):100553.

In conclusion, gender disparity still exists in clinical trials. This leads to lower participation rates of women, which puts their health at risk. These dynamics are driven by historical and socio-cultural biases, limited information and support during trials and a lack of awareness about gender differences in biomedical research.

As a key stakeholder in healthcare and a contributor to current and future clinical developments, pharmaceutical companies must play an active role in promoting gender equality and inclusivity in clinical trials. To do so, Alcimed can help you identify strategies and solutions to foster diversity in your clinical trials to advance health equity. This includes optimizing the design of clinical trials and enhancing patient engagement by identifying the specific information and support women need to improve recruitment and adherence. Don’t hesitate to contact our team!

About the authors,

Céline, Project Manager in the Healthcare team at Alcimed in France.

Johanna, Consultant in the Healthcare team at Alcimed in France.