Long or highly irregular menstrual cycles are a predictor of increased risk for type 2 diabetes mellitus (DM). This result comes from the Nurses Health Study II, in which 101073 American women aged 24-43 years were recruited in 1989, and followed for eight years. At baseline they self-reported on aspects of health, including family history, smoking, body mass index (BMI) and their menstrual cycle at age 18-22 years. Obesity was found to be a major risk factor for type 2 DM, but even after adjusting for BMI the relative risk of developing type 2 DM in women whose menstrual cycles were irregular or ≥ 40 days long was 2.08. Women with this menstrual history may benefit from lifestyle approaches to reduce risk.

