Why are women (still!) under-represented in medical research?

by Carolyn Thomas    ♥   Heart Sisters (on Blue Sky)

An article published in the journal Nature  (September 15, 2025) takes a hard look at why so few women are included in heart research.¹  This is not news. Clinical research in cardiovascular medicine has historically focused on male participants, often excluding women due to flimsy ethical, legal or regulatory issues.²  And I’ve been asking questions about this pervasive gender gap in cardiology ever since I survived a misdiagnosed widow-maker heart attack in my 50s.

Until 1993, in fact, many cardiovascular trials (such as the Physicians’ Health Study) included men only. In most cases, in fact, even laboratory studies included male animals only.

But how are those kinds of research results still being submitted, peer-reviewed, accepted and published in medical journals when they continue to ignore women – who, by the way make up over half of the population? When medical research focuses on the bodies of average (white, middle-aged) males – and then generalizes after the fact to apply theories to female bodies as well, it’s as if academic researchers believe that cardiac drugs, procedures, devices, and diagnostic tests that work in men will of course work exactly the same in women, who – after all – are just small men, right? 

Wrong! But as Dr. Janine Austin Clayton, associate director for women’s health research at the National Institutes of Health, said in a New York Times interview:

“We literally know less about every aspect of female biology compared to male biology.”

Emergency physician Dr. Alyson McGregor would immediately agree – just as she does in her compelling book, Sex Matters:  How Male-Centric Medicine Endangers Women’s Health and What We Can Do About It:  

The article in Nature also warns us that cardiovascular disease remains the leading cause of mortality among women globally. Yet females – particularly those who are older or non-white or pregnant or postpartum – remain profoundly under-represented in cardiovascular research. This  lack of growth in making heart research inclusive for all women underscores persistent research gaps, as the Nature article authors explain: 

“Greater efforts are needed across policy, funding and clinical trial design to ensure equitable representation of all women, particularly during vulnerable physiological stages to improve evidence-based cardiovascular care.”

Women already know that pregnancy, lactation and menopause involve significant hormonal and metabolic changes in our bodies – changes that are simply not captured in any research on male bodies. We can recognize that clinical trials done exclusively on men are generally irrelevant to women’s experiences, and vice versa.

These differences between men and women can affect our cardiovascular health, the way our female bodies metabolize the medications our doctors prescribe for us, and our uniquely female risk for dangerous heart conditions such as peripartum cardiomyopathy or disorders like preeclampsia and other pregnancy-related conditions associated with high blood pressure.  

The Nature authors warn that these conditions not only threaten maternal health, but also have significant implications for long-term cardiovascular risks in both mother and child^2,. They add that women remain routinely excluded from clinical trials, leaving our doctors relying on data from non-pregnant patients, which can lead to uncertainty in treatment decisions. 

Six of the all-female clinical trials listed in Nature also focused on menopause, yet no trials focused on Spontaneous Coronary Artery Dissection (SCAD). That absence is puzzling, because over 90 per cent of SCAD patients are females. According to cardiologist Dr. Sharonne Hayes, founder of the Mayo Women’s Heart Clinic and internationally respected SCAD expert, SCAD most commonly affects women in their 40s and 50s, although it can occur at any age, and can occur in men, too.  People who suffer a heart attack caused by SCAD are often fit, healthy women who don’t have the risk factors for heart disease you might expect, such as high blood pressure, high cholesterol or diabetes.⁴ 

See also:   How I Used to Describe SCAD, and What I’ve Learned Since Then.  

The Nature authors also found that cardiac research generally overlooks post-menopausal women, too – a group at significantly elevated heart disease risk³. Only a minority of trials noted in Nature included older women. But older women are also more likely to:

• have cardiac symptoms that differ from men’s
• experience adverse drug reactions
• respond differently to therapies than male patients 

Older women are often excluded due to other conditions like frailty or cognitive impairment, and even the historical academic emphasis on recruitment of younger, healthier study participants to reduce complexity and drop-outs during research projects. 

The Nature authors found that from 2017 to 2023, no significant increase was observed in either the number of all-female clinical trials or the total number of female participants enrolled in cardiovascular studies. They added: 

Those findings are consistent with previous research indicating women have historically made up only 20–35% of participants in major cardiovascular trials – yes, even in studies targeting heart conditions that predominantly affect women! 

How are clinical trials with such clearly lop-sided representation of female participants still being accepted by and published in medical journals as if these trials are relevant to women?  

See also:  Male-Centric Medicine: A Problem for Female Patients

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1. Pine, P.L.S. et al. “Enrollment of All-Female and Lactating or Pregnant Female Participants in Cardiovascular Trials. npj Cardiovascular Health 2, 46 (2025).

2. Tsang, W. et al. The Impact of Cardiovascular Disease prevalence on Women’s Enrollment in Landmark Randomized Cardiovascular Trials: a Systematic Review. ” J. Gen. Intern. Med. 27, 93–98 (2012).

3. Maas, A. H. E. M. et al. “Cardiovascular Health after Menopause Transition, Pregnancy Disorders, and Other Gynaecologic Conditions.  Eur. Heart J. 42, 967–984 (2021)  Eur. Heart J. 42, 967–984 (2021).

4. Khiatah, B. et al. Cardiovascular disease in women: a review of spontaneous coronary artery dissection. Medicines 101, e30433 (2022).

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NOTE FROM CAROLYN:  I wrote more about the known gender gap in cardiac research in my book, A Woman’s Guide to Living with Heart Disease  (Johns Hopkins University Press). You can ask for it at your public library or your favourite bookshop (please support your local independent booksellers) or order it online (paperback, hardcover or e-book) at Amazon – or order it directly from my publisher (use their code HTWN to save 30% off the list price).

ANOTHER NOTE FROM CAROLYN!   (Full disclosure):  Cardiologist Dr. Martha Gulati, one of the authors of the Nature article, also wrote the lovely and thoughtful foreword for my book.   ♥  Thank you, Dr. Martha!