Bad news for daily nappers. Taking long naps during the day has been linked to an increased risk of developing Type 2 diabetes, according to a review of past studies.

Researchers at the University of Tokyo reviewed 10 studies involving more than 260,000 peoples, looking for links between daytime sleepiness or napping and the risk of Type 2 diabetes, the Wall Street Journal reports.

They found that those who felt very sleepy during the day had a 56 percent higher risk of being diabetic than those who didn’t. Those who took naps of 60 minutes or more had a 46 percent higher risk of having the condition than those who took no or smaller naps.

The study, presented at the European Association for the Study of Diabetes conference in Stockholm, shows an association between the two conditions but doesn’t prove cause and effect.

Still, researchers say their findings suggest excessive sleepiness and long napping during the day may be a warning signal of Type 2 diabetes.