Background Sex and gender inequalities in ischemic heart diseases persist. Although ischemic heart disease is less common in women, they experience worse clinical outcomes and are less likely to receive guideline-recommended treatments. The primary scientific literature from which clinical guideline recommendations are derived may not have considered potential sex-and gender biases. This study aims to determine whether the literature cited in recent cardiovascular guidelines' clinical recommendations contain sex and gender biases. Methods We analysed publications cited in the 2019 European Society of Cardiology (ESC) guideline recommendations on chronic coronary syndromes, using a checklist to guide data extraction and evaluate the individual studies for sex-and gender-related aspects, such as inclusion/exclusion criteria, outcome measures, and demographic data reporting. To assess representation over time, the proportion of women participants in each study was computed and analysed using a beta regression model. We also examined the associations between women's representation, journal impact factor and author gender.

Findings Among the 20 ESC recommendations on chronic coronary syndromes, four contained sex-related statements; we did not identify any gender-specific suggestions. The referenced literature upon which these recommendations were based consisted of 108 articles published between 1991 and 2019, encompassing more than 1.6 million study participants (26.8%; 432,284 women). Only three studies incorporated sex-sensitive designs; none were gender-specific. The term "gender" did not occur in 84% (n = 91/108) of the publications; when used, it was exclusively to denote biological sex. The proportion of women (assumed by investigators) among study participants fluctuated over time. Having a woman as first (odds ratio (OR) = 1.68, 95% CI: 1.19-2.39) or last author (OR = 2.28, 95% CI: 1.31-3.97), was significantly associated with having more women participants in the study.

Interpretation The data underlying ESC guideline recommendations largely lack reporting of possible sex-and gender-specific aspects, and women are distinctly underrepresented. To what extent these recommendations apply to members of specific population groups who are not well-represented in the underlying evidence base remains unknown.