Skimping on sleep or overindulging in sleep might make diabetes more likely.

A study in Diabetes Care shows men who got little sleep (up to five or six nightly hours) or a lot of sleep (more than eight hours per night) were more likely to develop diabetes than men with moderate amounts of nightly sleep.

The study included more than 1,100 middle-aged and elderly men living in and around Boston. The researchers included H. Klar Yaggi, MD, MPH, of Yale University’s medical school.

Getting too much or too little sleep could be a risk factor for diabetes, Yaggi’s team reports.

Sleep and Diabetes

When the study started in the late 1980s, none of the men had diabetes.

They provided blood samples and were interviewed about their health habits, including their average hours of nightly sleep. Follow-up interviews were done in the mid-1990s and in 2002-2004.

Ninety new cases of diabetes were diagnosed during the study.

“Generally, those at the extremes in sleep duration [up to five hours and more than eight hours of sleep per night] had a worse risk profile in terms of diabetes risk than those who reported seven hours of sleep per night,” Yaggi and colleagues write.

They took into account other factors that boost diabetes risk. Even so, nightly hours of sleep mattered.

Seven Hours Ideal?

Seven hours of nightly sleep might be ideal for taming diabetes risk, the study suggests.

Compared to men who slept for seven hours per night, diabetes risk was twice as high for men reporting little nightly sleep (less than five or six hours) and three times as high for men reporting lots of sleep (more than eight hours per night).

Think of Goldilocks, the fictional character from fairy tales. She hunted for a bed that wasn’t too hard or too soft, and for porridge that wasn’t too hot or too cold. The “just right” level was Goldilocks’ goal, and if Yaggi’s study is right, seven hours of sleep might be “just right” for lowering diabetes risk.

However, Yaggi’s study doesn’t prove that sleep habits caused (or prevented) diabetes in any of the men. Men reporting seven hours of nightly sleep also tended to be younger, more educated, in better health, and had higher testosterone levels, the study shows.

They add that the effects of sleep on diabetes risk may be mediated by changes in testosterone. Other studies have shown that low testosterone has been associated with risk factors for diabetes including obesity, body fat distribution, and insulin resistance.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Yaggi, H. Diabetes Care, March 2006; vol 29: pp 657-661. Reuters.