Type 2 diabetes mellitus in women with polycystic ovary syndrome during a 24-year period: importance of obesity and abdominal fat distribution

STUDY QUESTION: What are the predictive factors for later development of type 2 diabetes (T2DM) in women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER: Obesity and abdominal fat distribution in women with PCOS in the mid-fertile years were the major risk factors for T2DM development 24 years later when lifestyle factors were similar to controls. WHAT IS KNOWN ALREADY: Women with PCOS have an increased prevalence of T2DM. STUDY DESIGN, SIZE, DURATION: A longitudinal and cross-sectional study was performed. Women with PCOS were examined in 1992 and in 2016. Randomly selected, age-matched women from the general population served as controls. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with PCOS (n=27), attending an outpatient clinical at a tertiary care centre for infertility or hirsutism were diagnosed in 1992 (mean age 30 years) and re-examined in 2016 (mean age 52 years). Women from the World Health Organization MONItoring of trends and determinants for CArdiovascular disease (WHO MONICA-GOT) 2008, aged 38-68 years, served as controls (n=94), and they were previously examined in 1995. At both at baseline and at follow-up, women had blood samples taken, underwent a clinical examination and completed structured questionnaires, and the women with PCOS also underwent a glucose clamp test at baseline. MAIN RESULTS AND THE ROLE OF CHANCE: None of women with PCOS had T2DM at baseline. At the 24-year follow-up, 19% of women with PCOS had T2DM versus 1% of controls (P<0.01). All women with PCOS who developed T2DM were obese and had waist-hip ratio (WHR) >0.85 at baseline. No difference was seen between women with PCOS and controls regarding use of high-fat diet, Mediterranean diet or amount of physical activity at follow-up at peri/postmenopausal age. However, women with PCOS had a lower usage of a high-sugar diet as compared to controls (P=0.01). The mean increases in BMI and WHR per year were similar in women with PCOS and controls during the follow-up period. LIMITATIONS, REASONS FOR CAUTION: The small sample size of women with PCOS and the fact that they were recruited due to infertility or hirsutism make generalization to women with milder forms of PCOS uncertain. WIDER IMPLICATIONS OF THE FINDINGS: Obesity and abdominal fat distribution, but not hyperandrogenism per se, in women with PCOS in the mid-fertile years were the major risk factors for T2DM development 24 years later when peri/postmenopausal. Lifestyle factors were similar to controls at that time.