The National Institutes of Health (NIH) Sex as a Biological Variable (SABV) policy aims to improve the rigor and reproducibility of biomedical research by encouraging sex-inclusive study designs and sex-based analyses. To evaluate policy implementation, we examine 574 funded publications (2017–2024) linked to grants from 21 NIH Institutes and Centers. We assess sex inclusion and sex-based reporting and analyses, while examining associations with author gender. Sixty-one percent of studies include both sexes, with human-subject research more likely to do so than non-human studies (p = 1.31×10-23). Of the single-sex studies, 34% focus on sex-specific topics. Among studies to include both sexes, 83% report sample sizes by sex, yet only 44% conduct sex-based analyses. Sex-based analyses are more common in human-subject studies (p = 0.00002) and in articles with women first authors (50% vs. 39%, p = 0.036). Articles with women as first and last author dyads are significantly more likely to analyze data by sex (OR = 2.24, 95% CI: 1.33–3.79). These findings suggest that while the SABV policy has encouraged sex inclusion, gaps remain in sex-based analyses. Author gender may influence these research practices, underscoring the need for continued efforts to fully integrate SABV into NIH-funded research studies. The U.S. National Institutes of Health (NIH) requires researchers to consider sex as a biological variable (SABV) to improve research quality and ensure findings benefit everyone. To assess how well this policy is being implemented, 574 NIH-funded publications from 2017–2024 were reviewed. Most studies (61%) included both sexes, particularly those involving humans. However, fewer than half (44%) analyzed results by sex, even when both sexes were included. Sex-based analyses were more common in human studies and in articles with women as first or senior authors. These findings show progress in sex inclusion, but many studies still fail to compare results by sex. Without these analyses, important differences may be missed. Stronger guidance and incentives are needed to ensure biomedical research fully considers sex and produces results that benefit all people. Warden et al. analyze 574 NIH-funded publications (2017–2024) to assess implementation of the Sex as a Biological Variable policy. They find that most studies include both sexes, but fewer than half analyze results by sex; such analyses are more common in human studies and when women are lead authors, highlighting persistent gaps in how sex is considered in biomedical research.
Warden et al. (Mon,) studied this question.