Abstract

Objectives

Medication taking is a complex multidimensional behavior that may be impeded by a range of biological and psychosocial factors, including sex and gender. We aimed to synthesize how sex and gender have been reported and analyzed in pharmacoepidemiologic studies of medication.

Methods

We searched for English-language peer-reviewed articles of observational studies (eg, cross-sectional, cohort, and case-control) that examined medication adherence among adults and included sex or gender in their reporting.

Results

We included 937 studies among 530 537 287 participants published between the year 1979 and 2021. Most studies were cross-sectional (47%), lasted ≤ 1 year (35%), examined self-reported adherence (53%), did not assess specific adherence problem(s) (40%), and included medications for cardiovascular conditions (24%) or systemic infections (24%). A quarter of studies (25%) used sex and gender interchangeably, more than one third of studies (36%) that reported gender data likely collected data on sex, and 1% of studies described sex and gender as distinct variables. Studies of cisgender participants more often reported that females/women experienced greater adherence problems often than males/men (31% vs 20%), particularly discontinuation and cost-related nonadherence. Only 21 studies (2%) reported on transgender individuals, and these predominantly examined antiretroviral medications for HIV.

Conclusions

Our review revealed substantial conflation of sex and gender in studies of medication adherence and a paucity of research among transgender individuals. Moreover, our synthesis showed sex/gender disparities in medication taking with studies reporting greater medication adherence problems among cisgender women and transgender participants than cisgender men.