Overweight and obese but not normal weight women with PCOS are at increased risk of Type 2 diabetes mellitus—a prospective, population-based cohort study

Abstract STUDY QUESTION What are the respective roles of polycystic ovary syndrome (PCOS), long-term weight gain and obesity for the development of prediabetes or Type 2 diabetes mellitus (T2DM) by age 46 years? SUMMARY ANSWER The risk of T2DM in women with PCOS is mainly due to overweight and obesity, although these two factors have a synergistic effect on the development of T2DM. WHAT IS KNOWN ALREADY PCOS is associated with an increased risk of prediabetes and T2DM. However, the respective roles of PCOS per se and BMI for the development of T2DM have remained unclear. STUDY DESIGN, SIZE, DURATION In a prospective, general population-based follow-up birth cohort 1966 (n = 5889), postal questionnaires were sent at ages 14 (95% answered), 31 (80% answered) and 46 years (72% answered). Questions about oligoamenorrhoea and hirsutism were asked at age 31 years, and a question about PCOS diagnosis at 46 years. Clinical examination and blood sampling were performed at 31 years in 3127 women, and at 46 years in 3280 women. A 2-h oral glucose tolerance test (OGTT) was performed at 46 years of age in 2780 women. PARTICIPANTS/MATERIALS, SETTING, METHODS Women reporting both oligoamenorrhoea and hirsutism at age 31 years and/or diagnosis of PCOS by 46 years were considered as women with PCOS (n = 279). Women without any symptoms at 31 years and without PCOS diagnosis by 46 years were considered as controls (n = 1577). The level of glucose metabolism was classified according to the results of the OGTT and previous information of glucose metabolism status from the national drug and hospital discharge registers. MAIN RESULTS AND THE ROLE OF CHANCE PCOS per se significantly increased the risk of T2DM in overweight/obese (BMI ≥ 25.0 kg/m2) women with PCOS when compared to overweight/obese controls (odds ratio: 2.45, 95% CI: 1.28–4.67). Normal weight women with PCOS did not present with an increased risk of prediabetes or T2DM. The increase in weight between ages 14, 31 and 46 years was significantly greater in women with PCOS developing T2DM than in women with PCOS and normal glucose tolerance, with the most significant increase occurring in early adulthood (between 14 and 31 years: median with [25%; 75% quartiles]: 27.25 kg [20.43; 34.78] versus 13.80 kg [8.55; 20.20], P < 0.001). LIMITATIONS, REASONS FOR CAUTION The diagnosis of PCOS was based on self-reporting, and the questionnaire at 46 years did not distinguish between polycystic ovaries only in ultrasonography and