Sex, Permanent Drug Discontinuation, and Study Retention in Clinical Trials

Background: Women are underrepresented across cardiovascular clinical trials. Whether women are more likely than men to prematurely discontinue study drug or withdraw consent once enrolled in a clinical trial is unknown. Methods: Eleven phase 3/4 TIMI (Thrombolysis in Myocardial Infarction) trials were included (135 879 men and 51 812 women [28%]). The association between sex and premature study drug discontinuation and withdrawal of consent were examined by multivariable logistic regression after adjusting for potential confounders in each individual trial and combining the individual point estimates in random effects models. Results: After adjusting for baseline differences, women had 22% higher odds of premature drug discontinuation (adjusted odds ratio [OR adj ], 1.22 [95% CI, 1.16–1.28]; P <0.001) compared with men. Qualitatively consistent results were observed for women versus men in the placebo arms (OR adj , 1.20 [95% CI, 1.13–1.27]) and active therapy arms (OR adj , 1.23 [95% CI, 1.17–1.30)]; there was some evidence for regional heterogeneity ( P interaction <0.001). Of those who stopped study drug prematurely, a similar proportion of men and women in the active arm stopped because of an adverse event (36% for both; P =0.60). Women were also more likely to withdraw consent compared with men (OR adj , 1.26 [95% CI, 1.17–1.36]; P <0.001). Conclusions: Women were more likely than men to prematurely discontinue study drug and withdraw consent across cardiovascular outcome trials. Premature study drug discontinuation was not explained by baseline differences by sex or a higher proportion of adverse events. Future trials should better capture reasons for drug discontinuation and withdrawal of consent to understand barriers to continued study drug use and clinical trial participation, particularly among women.