Getting too little -- or too much -- sleep may increase a person's risk of developing type 2 diabetes, new research suggests.
"Sleep duration may be a novel risk factor for the development of clinical diabetes," conclude the researchers in the March issue of Diabetes Care.
Dr. Henry Klar Yaggi from Yale University in New Haven, Conn. and two colleagues studied the long-term (15-year) impact of sleep duration on the development of diabetes in more than 1,100 middle-aged and elderly men who were free of diabetes in 1987-1989 and were followed until 2004.
Men getting no more than 6 hours of sleep per night, as well as those getting more than 8 hours of shut eye per night, were at significantly increased risk for developing diabetes, compared to men getting 7 to 8 hours of sleep each night.
The risk of diabetes was roughly twofold higher in men reporting short sleep duration and more than threefold higher in those reporting long sleep duration, compared with men sleeping 7 to 8 hours nightly.
"This U-shaped distribution of risk with respect to sleep duration has been reported previously for coronary heart disease, all cause mortality, and diabetes in women," Yaggi told Reuters Health.
The elevated risks with short or long durations of sleep "remained essentially unchanged" after adjustment for several factors including age, blood pressure, smoking status and waist circumference, the authors say.
However, relative risks were reduced "considerably" when adjusted for testosterone, suggesting to the team that the effects of sleep on diabetes could be mediated via changes in the body's levels of this hormone.