Persistent under-representation of female patients in United States trials of common vascular diseases from 2008 to 2020.

Abstract Background Women have been historically under-represented in vascular surgery and cardiovascular medicine trials. The rate and change in representation of women in trials of common vascular diseases over the last decade is not understood completely. Methods We used publicly available data from ClinicalTrials.gov to evaluate trials pertaining to carotid artery stenosis (CAS), peripheral arterial disease (PAD), thoracic and abdominal aortic aneurysms (TAA and AAA), and type B aortic dissections (TBAD) from 2008 to the present. We evaluated representation of women in these trials based on the participation-to-prevalence ratios (PPR), which are calculated by dividing the percentage of women among trial participants by the percentage of women in the disease population. Values of 0.8 to 1.2 reflect similar representation. Results The sex distribution was reported in all 97 trials, including 11 CAS trials, 68 PAD trials, 16 TAA/AAA trials, and 2 TBAD trials. The total number of participants in these trials was 41,622 and the median number of participants per trial was 150.5 (interquartile range [IQR], 50-252). The percentage of women in the disease population was 51.9% for CAS, 53.1% for PAD, 34.1% for TAA/AAA, and 30.9% for TBAD. Industry sources funded 76 of the trials (77.6%), and the Veterans Affairs Administration (n = 4 [4.1%]), unspecified university (n = 7 [7.1%]), and extramural sources (n = 11 [11.2%]) funded the remainder of the trials. The overall median PPR for all four diseases was 0.65 (IQR, 0.51-0.80). Women were under-represented for all four conditions studied (CAS, 0.73 [IQR, 0.62-0.96]; PAD, 0.65 [IQR, 0.53-0.77]; TAA/AAA, 0.59 [IQR, 0.38-1.20]; and TBAD, 0.74 [IQR, 0.65-0.84]). There was no significant difference in PPR among the diseases (P = .88). From 2008 to the present, there was no significant change in PPR values over time overall (r2 = 0.002; P = .70). When examined individually, PPR did not change significantly over time for any of the diseases studied (for each, r2  .45). The PPR did not vary significantly over time for any of the funding sources (for each, r2  .08). There was appropriate representation (PPR of 0.8-1.2) in a minority of trials for each disease except TBAD (CAS, 27.3%; PAD, 15.9%; TAA/AAA, 18.8%; and TBAD, 50%). Trials that were primarily funded from university sources had the highest median PPR (1.04; IQR, 0.21-1.27), followed by industry-funded (0.67; IQR, 0.54-0.81), and extramurally funded (0.60; IQR, 0.34-0.73). Studies funded by Veterans Affairs had the lowest PPR (0.02; IQR, 0.00-0.11; P = .004). Conclusions Participation of women in US trials of common vascular diseases remains low and has not improved since 2008. Therefore, the generalizability of recent trial results to women with these vascular diseases remains unknown. An improved understanding of the underlying root causes for poor female trial participation, advocacy, and education are required to improve the generalizability of trial results for female vascular patients.