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

Short-term partial sleep restriction results in glucose intolerance and insulin resistance. The purpose of this study was to assess the long-term relationship between sleep duration and the incidence of clinical diabetes.

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: < or =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.

Men reporting short sleep duration (< or =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 < or =5 h and 3.12 [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 < or =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.

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.