Research Letter
October 30, 2023
Gender Gap in Leadership of Clinical Trials
Ithai Waldhorn, David Bomze, Irit Ben-Aharon, et al
JAMA Intern Med. Published online October 30, 2023. doi:10.1001/jamainternmed.2023.5104
Clinical trials provide the highest-quality evidence and remain the bedrock for clinical decision-making. They require participation of numerous patients, enormous resources, and substantial funding. Serving as a principal investigator (PI) can lead to professional advancements and prestige, making it a significant career advancement opportunity for physicians.
Methods
In this cross-sectional study, ClinicalTrials.gov was queried for trials conducted between January 2005 and May 2023. According to Israeli Ministry of Health guidelines, institutional review board approval and participant informed consent were not required since this study used publicly available, deidentified aggregate participant data. We followed the STROBE reporting guideline.
We assessed representation of women as PIs with gender predicted using Genderize.io (eAppendix in Supplement 1). The Cochran-Armitage trend test was used to estimate the association between representation of women PIs over time and study phases. The association between gender of the PI and trial participants was evaluated using the Wilcoxon rank sum test. Data were analyzed using R, version 4.0.3. Two-sided P < .05 was significant.
Results
Among 245 771 unique eligible trials, gender could be determined for 277 993 of 290 078 PIs (95.8%). In total, 93 906 PIs (32.4%) were women and 184 087 (63.5%) were men. We found the lowest proportions of women PIs for cardiology (20.3%) and hepatology (21.4%) and the highest for rheumatology (49.2%) and obstetrics-gynecology (43.9%) (Figure 1). Fewer trials led by women were funded by the biomedical industry (19.2%) compared with nonindustry trials (39.5%) (odds ratio [OR], 0.38; 95% CI, 0.36-0.40; P < .001). The proportion of women PIs significantly increased over the study period from 27.0% in 2005 to 39.6% in 2023 (P < .001).
Analysis by study type identified a lower rate of women PIs in interventional vs observational trials (26.8% vs 32.0%; OR, 0.78 [95% CI, 0.76-0.80]; P < .001). An association between trial phase and proportion of women PIs was found, with lower proportions of women PIs in later-phase trials (phase 1, 28.5%; phase 2, 27.5%; phase 3, 25.9%; and phase 4, 24.7%; P < .001). Analysis by geographic distribution revealed greater representation of women among PIs in North America (35.4%) and Europe (30.1%) vs Asia (26.5%) (Figure 2). Women vs men leadership was more common in trials with greater representation of women as study participants (52.5% vs 47.5%; P < .001), even after excluding gender-specific studies (49.4% vs 46.4%; P < .001).
Discussion
Half of medical students and residency populations in the US and 37% of active physicians are women.1 However, underrepresentation of women remains prevalent in science and medicine. Prior work examined field-specific representation of women among PIs.2,3 In this study, we observed persistent underrepresentation of women PIs despite a growing percentage over time. The gender gap was more pronounced in late-phase and industry-funded trials. Greater enrollment of women as study participants was found in trials led by women. Understanding factors associated with disproportional leadership by gender among specific subsets of trials is key to addressing disparities in clinical research. Our study is in line with previous studies showing an achievement gap between men and women faculty in career advancement, leadership opportunities, financial compensation, and scientific recognition.4-6
A limitation is that we did not account for the proportions of academic physicians by gender based on period, geographic location, or specialty, and these may reflect some of the associations observed. We also did not explore nonbinary gender. We used validated methods to determine PI gender, but misclassifications may have occurred.
These data may serve as a benchmark for women leadership of clinical trials across medicine, identifying covariates and trial subsets associated with differential representation of women. While the proportion of women leading trials has increased over time, efforts to understand and address underpinnings of disparities in trial leadership are necessary.
