Long Menstrual Cycle Is Associated with Type 2 Diabetes Mellitus in Korean Women

BACKGROUND Long menstrual cycle is a risk factor for developing type 2 diabetes and cardiovascular disease in women. We aimed to evaluate the association between existing type 2 diabetes and oligomenorrhea before diagnosis of diabetes, and to observe the differences in this association among obese and non-obese Korean women. METHODS Patients with type 2 diabetes (n=118) and without any clinical evidence of abnormal glucose regulation (n=258) who attended the outpatient clinic of a university hospital and were over age 30. Patients self-reporting a menstrual cycle over 40 days during their 20s were defined as oligomenorrhea before diagnosis of diabetes. Obesity was defined as having a body mass index (BMI) over 25 kg/m(2). RESULTS The frequency of oligomenorrhea before diagnosis of diabetes was almost two-fold higher in women with type 2 diabetes than in the control group (16.1% vs. 8.5%, P=0.03). Oligomenorrhea was associated with type 2 diabetes after adjusting for age, BMI, systolic blood pressure, triglycerides, and high density lipoprotein cholesterol (odds ratio, 3.89; 95% confidence interval, 1.37 to 11.04). Among women with oligomenorrhea before diagnosis of diabetes, the frequency of type 2 diabetes was significantly higher in obese subjects than in their non-obese counterparts (90.9% vs. 30.0%, P=0.03). CONCLUSION Having a long menstrual cycle could be a risk factor for the development of type 2 diabetes, especially in obese women.