Figure 1. Sex Bias in Clinical Studies Over Time Determined From Published Articles for Cardiovascular Diseases, Diabetes, Digestive Diseases, and Hepatitis (Types A, B, C, and E).

An intercept-only linear model was fitted to sex bias values from before and during 1993 and subsequently in 5-year increments. Estimated sex bias intercept coefficients were plotted against time for studies (blue) and participants as measurement unit (orange), with error bars representing 95% confidence intervals for the mean coefficients. The points for total at the right of each graph represent the mean sex bias totals for each category. Sex bias was defined as female participant fraction (determined separately for studies and participants as measurement unit) minus female prevalence fraction (values for sex bias ranged from −1 to 1, with 0 indicating no bias; negative sex bias indicates that female participants were represented less than male participants).

^aDifference between sex bias value vs 0; P < .001 for studies as measurement unit.

^bDifference between sex bias value vs 0; P < .001 for participants as measurement unit.