Representation of Women in Randomized Trials in Cardiac Surgery: A Meta-Analysis

Background Women have traditionally been underrepresented in randomized clinical trials (RCTs). We performed a systematic evaluation of the inclusion of women in cardiac surgery RCTs published in the past 2 decades. Methods and Results MEDLINE, EMBASE, and the Cochrane Library were searched (2000 to July 2020) for RCTs written in English, comparing ≥2 adult cardiac surgical procedures. The percentage of women enrolled and its association with year of publication, sample size, mean age, funding source, geographic location, number of sites involved, and interventions tested were analyzed using a meta-analytic approach. Fifty-one trials were included. Of 25 425 total patients, 5029 were women (20.8%; 95% CI, 17.6-24.4; range, 0.5%-57.9%). The proportion of women dropped significantly during the study period (29.6% in 2000 versus 13.1% in 2019, P<0.001). Women were significantly more represented in European trials (26.2%; 95% CI, 21.2-31.9), and less represented in trials of coronary bypass surgery versus other interventions (16.8%; 95% CI, 12.3-22.7 versus 33.6%; 95% CI, 27.4-40.5; P=0.0002) and in trials enrolling younger patients (P=0.009); the percentage of women was higher in industry-sponsored versus non-industry sponsored trials (31.7%; 95% CI, 27.2-36.6 versus 15.5%; 95% CI, 10.0-23.2; P=0.0004) and was not associated with trial sample size (P=0.52) or study design (multicenter versus monocenter: P=0.22). After exclusion of trials conducted at Veteran Affairs centers, women representation was 24.4% (95% CI, 21.1-28.0; range, 10.4%-57.9%), with no significant changes during the study period. Conclusions The proportion of women in cardiac surgery trials is low and likely inadequate to provide meaningful estimates of the treatment effect.