Sleep duration as a risk factor for the development of type 2 diabetes

OBJECTIVE - Short-term partial sleep restriction results in glucose intolerance and insulin 0 resistance. The purpose of this study was to assess the long-term relationship between sleep duration and the incidence of clinical diabetes. RESEARCH DESIGN AND METHODS - A cohort of men from the Massachusetts Male Aging Study without diabetes at baseline (1987-1989) were followed until 2004 for the development of diabetes. Average number of hours of sleep per night Was grouped into the following categories: <= 5, 6, 7, 8, and > 8 h. Incidence rates and relative risks (RRs) were calculated for the development of diabetes in each sleep duration category. Those reporting 7 h of sleep per night served as the reference group. Multivariate analysis was performed using Poisson regression. RESULTS - Men reporting short sleep duration (<= 5 and 6 h of sleep per night) were twice as likely to develop diabetes, and men reporting long sleep duration (> 8 h of sleep per night) were more than three times as likely to develop diabetes over the period of follow-up. Elevated risks remained essentially unchanged after adjustment for age, hypertension, smoking status, self-rated health status, education, and waist circumference (RR 1.95 [95% CI 0.95-4.01] for <= 5 IT and 3.1.2 [1.53-6.37] for > 8 h). RRs were altered considerably for the two extreme sleep groups when adjusted for testosterone (1.51 [0.71-3.19] for <= 5 h and 2.81 [.1.34-5-90] for > 8 h), suggesting that the effects of sleep on diabetes could be mediated via changes in endogenous testosterone levels. CONCLUSIONS - Short and long sleep durations increase the risk of developing diabetes, independent of confounding factors. Sleep duration may represent a novel risk factor for diabetes.