Risk of Type 2 Diabetes Among Lesbian, Bisexual, and Heterosexual Women: Findings From the Nurses’ Health Study II

OBJECTIVE Lesbian and bisexual (LB) women are more likely than heterosexual women to exhibit risk factors for type 2 diabetes, but studies estimating the burden of type 2 diabetes among LB women are uncommon and limited to cross-sectional designs. This study investigated incidence of type 2 diabetes in LB women and heterosexual women in a large, longitudinal U.S. cohort. RESEARCH DESIGN AND METHODS Women participating in the Nurses’ Health Study II (NHS II) ages 24–44 years in 1989 were prospectively followed through 2013. Self-reported clinician diagnosis of type 2 diabetes was assessed every other year to identify incidence. Of the participants, 1,267 identified as lesbian or bisexual and 92,983 identified as heterosexual. Cox proportional hazards regression was used to model incidence of type 2 diabetes. RESULTS LB women had a 27% higher risk of developing type 2 diabetes than heterosexual women (adjusted incidence rate ratio [IRR] 1.27, 95% CI 1.05, 1.54). Differences between LB women and heterosexual women in risk of type 2 diabetes were greater during younger ages (sexual orientation–by-age interaction, P < 0.001). BMI mediated the relationship between sexual orientation and type 2 diabetes; the IRR was completely attenuated when BMI was added to the model (IRR 0.85, 95% CI 0.70, 1.03). CONCLUSIONS Findings indicate that LB women develop type 2 diabetes at younger ages than heterosexual women. Higher BMI in LB women is an important contributor to this disparity. Public health and clinical efforts to prevent, detect, and manage obesity and type 2 diabetes among LB women are warranted.