Gender Bias in Clinical Trial Enrollment: Female Authorship Matters

Despite initiatives to promote equal enrollment of human subjects in clinical trials, females continue to be underrepresented. The goal of this work is to determine if female enrollment in human clinical trials published in 3 high-impact journals from 2015 to 2019 is correlated with gender of first and/or senior authors.

Clinical trials published in the Journal of the American Medical Association (JAMA), The Lancet, and the New England Journal of Medicine (NEJM) from January 1, 2015, to December 31, 2019, were reviewed. Trials were excluded for ongoing enrollment, sex-specific disease research, or author name without gender assignment. One-sample χ² pairwise comparisons and two-tailed proportion tests on the proportion of females between gender author pairings were done overall and for each subset analysis.

In total, 1,427 articles enrolled a total of 2,104,509 females and 2,616,981 males (44.6% vs. 55.4%, P ≤ 0.0001) in clinical trials. Overall, more females were enrolled if both first and senior authors were female (51.7% vs. 48.3%, P ≤ 0.0001). Proportion of females enrolled decreased with the following first and senior author pairings: female-male (48.9%), male-female (48.6%), and male-male (40.5%, P ≤ 0.0001 compared to female-female authorship). Greater female enrollment in clinical trials with female-female compared to male-male authorship persisted in subset analyses by funding source, phase, randomization for study participants, drug and/or device trial, and geographic location. Female enrollment was higher in 3 surgical specialties: neurosurgery (all authors: 52%, P ≤ 0.01), ophthalmology (all authors: 53.6%, P ≤ 0.0001), and surgery (all authors: 54.4%, P ≤ 0.0001). The majority of surgical specialties did not publish trials with female-female authorship but when stratifying by author gender pairing, surgical oncology had the highest female enrollment with female-female authorship (98.4%, P ≤ 0.0001).

Female authorship of clinical trial publications, specifically having both first and senior authors as female, was correlated with higher female enrollment in clinical trials when compared to male authorship and endured with multiple subset analyses.