Incidence of Autoimmune Diseases in 30,340 Danish Women With Polycystic Ovary Syndrome (PCOS) Compared to 151,520 Controls. A National Cohort Study.

Autoimmunity can be part of the pathogenesis of polycystic ovary syndrome (PCOS), but prospective studies on autoimmune disease in population based cohorts are lacking. This study aimed to investigate incidence rates of autoimmune disease in Danish women with PCOS before and after PCOS diagnosis compared to controls. National register-based study. Danish women diagnosed with PCOS (N = 30,340) and age-matched controls (N = 151,520). Autoimmune disease was study outcome (defined by ICD10 diagnosis for autoimmune diseases and/or medical treatment for type 1 diabetes (T1D) or thyroid disease). The median age at PCOS diagnosis was 29 years (interquartile range (IQR), 23; 36). BEFORE PCOS DIAGNOSIS: (Mean risk time 11.3 years until PCOS diagnosis), the incidence rate ratio (IRR) for all autoimmune diseases was 1.52 (1.45; 1.59) in women with PCOS compared to controls, for T1D 2.31 (2.06; 2.59) and for thyroid disease 1.72 (1.61; 1.84), p < 0.001. DURING FOLLOW UP: (After PCOS diagnosis, mean follow up duration 9.8 years), women with PCOS compared to controls had IRR for autoimmune disease of 1.50 (1.44; 1.57), T1D of 3.49 (3.16; 3.87) and thyroid disease of 1.48 (1.40; 1.57), all p < 0.001. In women with PCOS, higher incidence of autoimmune disease before and after PCOS diagnosis was related to foreign ethnicity, low family income, comorbidity, infertility, and higher BMI. The incidence rate of autoimmune disease was higher in women with PCOS compared to controls, before and after PCOS diagnosis, and this higher incidence was associated with lower socioeconomic status, comorbidity and higher BMI. Not applicable.