Daytime sleepiness and taking long naps during the day may both be associated with an increased risk for type 2 diabetes, according to a meta-analysis presented at EASD 2015, the annual meeting of the European Association for the Study of Diabetes.

Specifically, researchers reported that excessive daytime sleepiness appeared to increase the risk for diabetes by 56%, and a daytime nap of 60 minutes or more appeared to increase this risk by 46%. 

“This research cannot prove causality. Short naps might have beneficial effects on diabetes, although we have to acknowledge the possibility of ‘reverse causality’ and the mechanisms are still unclear,” said study researcher Tomohide Yamada, MD, PhD, of the department of diabetes and metabolic diseases at the University of Tokyo in Japan.

Yamada, who presented the study findings, said results showed that a shorter nap of 60 minutes or less per day did not increase the risk for diabetes, and there was no effect of napping up to about 40 minutes per day, after which risk began to increase sharply.

Excessive daytime sleepiness is widely prevalent around the world, as is the habit of taking short sleeps or “napping.” Daytime naps are usually brief, but can range from a few minutes to a few hours. The frequency varies from taking an occasional nap to planned rest periods several times daily for habitual nappers.

Some individuals take a nap because they are excessively sleepy during the daytime as a result of a sleep disorder. Yamada said it is important to look at this issue to help identify factors such as sleep deficits and sleep apnea, which may be increasing diabetes risk.

This article originally appeared on Endocrinology Advisor