Can Naps Lead to Type 2 Diabetes?

WESTCHESTER, Ill. -- Admit it. There's nothing like taking that quick cat nap in the middle of the day. It rejuvenates your mind and gives you a fresh burst of energy. But beware: a new study in the March 1 issue of the journal Sleep shows that frequent daytime napping may increase your risk of of type 2 diabetes.

The study looked at an older Chinese population and found that the prevalence of type 2 diabetes was 36 percent higher in participants who reported napping four to six times a week and 28 percent higher in those who napped daily.

Similar associations were found between napping and impaired fasting glucose. The observed associations were unaltered in statistical analyses that removed participants with potential ill health and daytime sleepiness, suggesting it is less likely that diabetes leads to daytime sleepiness and raising the possibility that napping may increase the risk of diabetes.

According to the authors, napping in China is a social norm, which is practiced by all ages primarily as a habit started in childhood. In Western countries, napping is less common and is often unplanned and prompted by sleepiness likely caused by aging, deteriorating health status or nighttime complaints.

Lead author Neil Thomas, PhD, reader in epidemiology at the University of Birmingham, U.K., said that additional research is needed to determine if napping itself plays a causative role in the development of type 2 diabetes, or if other factors are involved.

"In many non-Mediterranean, Western countries a large proportion of those that nap are generally older or have other conditions that cause tiredness and create an urge to nap," said Thomas. "The napping can therefore be a marker of disease."

The authors noted that the association between napping and diabetes was observed despite the fact that nappers had higher levels of physical activity, which has been shown to reduce the risk of diabetes. This suggests that the relationship between napping and diabetes might have been stronger had it not been offset by the protective effects of physical activity.