Study Examines Gender Differences in Participation in Clinical Trials Compared to Those Affected by a Disease

For much of medical history, women were largely excluded from clinical trials. Now research funded by the National Institutes of Health is mandated to have gender equity in participants in clinical trials. But a new study by scholars at Northwestern University, Harvard University, and Stanford University that cross-analyzed 20,020 U.S. clinical trials between 2000 and 2020 found that women are underrepresented in clinical trials in cardiology, oncology, neurology, immunology, and hematology. Meanwhile, men are underrepresented in clinical trials in musculoskeletal disease and trauma, psychiatry, and preventive medicine.

The authors state that clinical trial sample populations should be proportionate to the population affected by the disease, as some diseases are more prevalent or manifest differently in one sex versus the other.  The study is the first to examine sex bias in all U.S. human clinical trials relative to disease burden (the prevalence of disease based on factors such as sex and ethnicity).

“Sex bias in clinical trials can negatively impact both men and women by creating gendered data gaps that then drive clinical practice,” said Jecca Steinberg, a medical resident in the department of obstetrics and gynecology at Northwestern University Feinberg School of Medicine and the lead author of the study. “Neglecting one sex in clinical trials — the gold standard scientific exploration and discovery — excludes them from health innovation and skews medical evidence toward therapies with worse efficacy in that sex.”

Underrepresentation of either sex in clinical trials can be associated with suboptimal health outcomes, as men and women experience differences in medical test results, disease progression, treatment response, drug metabolism, and surgical outcomes, Dr. Steinberg said. Participating in clinical trials is one of the only ways to access new, innovative treatments and therapies – especially in the field of oncology – so the relative deficiency of one sex contributes to disparities in health outcomes.

The full study, “Analysis of Female Enrollment and Participant Sex by Burden of Disease in US Clinical Trials Between 2000 and 2020,” was published on JAMA Open Network. It may be accessed here.