Aims/hypothesis: The objective of this study was to investigate the association between laparoscopically confirmed endometriosis and risk of type 2 diabetes.
Methods: We used data from the Nurses' Health Study II, a prospective cohort of female nurses followed for >25 years (N = 112,037). We used Cox proportional hazards models to estimate the HRs and 95% CIs of incident, confirmed type 2 diabetes (n = 8496 participants) adjusted a priori for confounding factors. We additionally investigated differences in the relationship between endometriosis and type 2 diabetes by age (<50 or ≥50 years), BMI (<30 or ≥30 kg/m2), infertility history, menopausal status and history of gestational diabetes mellitus (GDM; restricted to parous women).
Results: We saw no association between laparoscopically confirmed endometriosis and risk of type 2 diabetes in multivariable confounder-adjusted models (HR 1.06 [95% CI 0.98, 1.13]) or models accounting for potential mediating factors (HR 0.94 [95% CI 0.87, 1.00]). However, we observed modest differences in the association between endometriosis and type 2 diabetes by BMI group, history of infertility and history of GDM. Among non-obese women (HR 1.17 [95% CI 1.02, 1.35]), women who never experienced infertility (HR 1.14 [95% CI 1.04, 1.25]) and women who never experienced GDM (HR 1.11 [95% CI 1.01, 1.22]), endometriosis was associated with greater risk of type 2 diabetes.
Conclusions/interpretation: Overall, women with endometriosis were not at increased risk of type 2 diabetes. However, among subgroups at low risk for type 2 diabetes (i.e. non-obese women and women with no prior history of infertility or GDM), endometriosis was associated with a modest increased risk of type 2 diabetes.
Keywords: Diabetes; Endometriosis; Epidemiology; Gestational diabetes.