Disparities in Mortality by Sexual Orientation in a Large, Prospective Cohort of Female Nurses

IMPORTANCE: Extensive evidence documents health disparities for lesbian, gay, and bisexual (LGB) women, including worse physical, mental, and behavioral health than heterosexual women. These factors have been linked to premature mortality, yet few studies have investigated premature mortality disparities among LGB women and whether they differ by lesbian or bisexual identity. OBJECTIVE: To examine differences in mortality by sexual orientation. DESIGN, SETTING, AND PARTICIPANTS: This prospective cohort study examined differences in time to mortality across sexual orientation, adjusting for birth cohort. Participants were female nurses born between 1945 and 1964, initially recruited in the US in 1989 for the Nurses’ Health Study II, and followed up through April 2022. EXPOSURES: Sexual orientation (lesbian, bisexual, or heterosexual) assessed in 1995. MAIN OUTCOME AND MEASURE: Time to all-cause mortality from assessment of exposure analyzed using accelerated failure time models. RESULTS: Among 116 149 eligible participants, 90 833 (78%) had valid sexual orientation data. Of these 90 833 participants, 89 821 (98.9%) identified as heterosexual, 694 (0.8%) identified as lesbian, and 318 (0.4%) identified as bisexual. Of the 4227 deaths reported, the majority were among heterosexual participants (n = 4146; cumulative mortality of 4.6%), followed by lesbian participants (n = 49; cumulative mortality of 7.0%) and bisexual participants (n = 32; cumulative mortality of 10.1%). Compared with heterosexual participants, LGB participants had earlier mortality (adjusted acceleration factor, 0.74 [95% CI, 0.64-0.84]). These differences were greatest among bisexual participants (adjusted acceleration factor, 0.63 [95% CI, 0.51-0.78]) followed by lesbian participants (adjusted acceleration factor, 0.80 [95% CI, 0.68-0.95]). CONCLUSIONS AND RELEVANCE: In an otherwise largely homogeneous sample of female nurses, participants identifying as lesbian or bisexual had markedly earlier mortality during the study period compared with heterosexual women. These differences in mortality timing highlight the urgency of addressing modifiable risks and upstream social forces that propagate and perpetuate disparities.