If you nap for more than an hour each day it could be a warning sign you have Type 2 diabetes, scientists have suggested.
The Japanese researchers found that people who nap for 60 minutes or more each day have a 45% increased chance of diabetes than people who do not nap.
However, they stressed that there is no evidence napping directly causes diabetes. Instead, they suggested that napping may be a warning sign of the disease.
The researchers, from the University of Tokyo, analysed data from 21 studies involving more than 300,000 people to draw their conclusions.
Each of the participants had recorded their daily levels of napping and been tested for Type 2 diabetes.
While the scientists found that people who napped for more than one hour each day were the most likely to have diabetes, they also found that napping for under 40 minutes had no impact on diabetes diagnosis.
The researchers, who presented their findings at the European Association for the Study of Diabetes, said long naps could be a sign of sleep deprivation at nighttime, which could be the root cause of Type 2 diabetes.
They pointed out that when we are tired, we tend to have an increased appetite and reach for sugary foods to give us energy. This, in turn, can increase our risk of Type 2 diabetes.
Commenting on the findings, Professor Naveed Sattar, of the University of Glasgow, said more work needs to be done before we can draw firm conclusions around the links between napping and diabetes.
“This observational study shows an association between longer naps and diabetes. It’s likely that risk factors which lead to diabetes also cause napping. This could include slightly high sugar levels meaning napping may be an early warning sign of diabetes,” he said, according to The Telegraph.
“That said, there is now abundant evidence of a link of sorts between sleep disturbances and diabetes. What we need are trials to determine if, when and for how long one sleeps makes a difference to real health outcomes. Trials bring truth and without proper trials, we simply will never know the answer.”
Dr Benjamin Cairns, from the Cancer Epidemiology Unit at University of Oxford, added that it’s unclear whether napping causes diabetes, or whether sleepiness is a symptom of diabetes.
“One particular difficulty in observational studies of daytime napping is that people with long-term diseases, like diabetes, often feel tired during the day due to their illness,” he said, according to Science Media Centre.
“This can even occur before they are diagnosed, so it can falsely appear that their illness followed increased napping, rather than the other way around. In research studies, this could mean that longer naps appear to cause diabetes or other diseases, even when only the reverse is true.”