Impaired glucose tolerance, type 2 diabetes and metabolic syndrome in polycystic ovary syndrome: a systematic review and meta-analysis

Polycystic ovary syndrome (PCOS) is a common condition in reproductive-aged women associated with impaired glucose tolerance (IGT), type 2 diabetes mellitus (DM2) and the metabolic syndrome. A literature search was conducted (MEDLINE, CINAHL, EMBASE, clinical trial registries and hand-searching) identifying studies reporting prevalence or incidence of IGT, DM2 or metabolic syndrome in women with and without PCOS. Data were presented as odds ratio (OR) [95% confidence interval (CI)] with fixed- and random-effects meta-analysis by Mantel–Haenszel methods. Quality testing was based on Newcastle–Ottawa Scaling and The Cochrane Collaboration's risk of bias assessment tool. Literature searching, data abstraction and quality appraisal were performed by two investigators. A total of 2192 studies were reviewed and 35 were selected for final analysis. Women with PCOS had increased prevalence of IGT (OR 2.48, 95% CI 1.63, 3.77; BMI-matched studies OR 2.54, 95% CI 1.44, 4.47), DM2 (OR 4.43, 95% CI 4.06, 4.82; BMI-matched studies OR 4.00, 95% CI 1.97, 8.10) and metabolic syndrome (OR 2.88, 95% CI 2.40, 3.45; BMI-matched studies OR 2.20, 95% CI 1.36, 3.56). One study assessed IGT/DM2 incidence and reported no significant differences in DM2 incidence (OR 2.07, 95% CI 0.68, 6.30). One study assessed conversion from normal glucose tolerance to IGT/DM2 (OR 2.4, 95% CI 0.7, 8.0). No studies reported metabolic syndrome incidence. Women with PCOS had an elevated prevalence of IGT, DM2 and metabolic syndrome in both BMI and non-BMI-matched studies. Few studies have determined IGT/DM2 or metabolic syndrome incidence in women with and without PCOS and further research is required.