Napping is generally viewed as a harmless, if somewhat indulgent, practice in the United States. Unlike in many other countries where an afternoon siesta is common, there is no ingrained culture of napping here. But the results of a study from a country where napping is more common — China — don’t bode especially well for the practice, pointing to a link between longer naps and a higher risk of Type 2 diabetes.
The study, published in the October 2013 issue of the journal Sleep Medicine, looked at over 27,000 adults age 45 and above who had retired from their jobs. According to an article on the study in Britain’s Daily Mail, researchers at Huazhong University of Science and Technology asked study participants about their daily napping habits and assigned each person to one of four categories based on their response: a nap lasting less than 30 minutes, 30–59 minutes, 60–89 minutes, or 90 or more minutes each day. About 70% of participants said they took a daily nap; those who did not were put in the “less than 30 minutes” category. Each participant also had his or her blood pressure, cholesterol, and fasting plasma glucose level measured.
Even after adjusting for factors such as age and health history that could affect a participant’s risk of developing prediabetes or Type 2 diabetes, the researchers found that longer napping was associated with a higher risk of both of these conditions. A higher risk of prediabetes was seen starting at a nap duration of 60 minutes, with the risk level increasing along with a longer nap duration. A higher risk of Type 2 diabetes was seen starting at a nap duration of 30 minutes, and this risk level also increased with nap duration, with the exception that no increased risk was seen in the 60–89-minute group. Forty percent of regular nappers had elevated blood pressure, compared with 33% of those who didn’t nap, while 24% of nappers had elevated cholesterol, compared with 19% of abstainers.
This study does not definitively prove, of course, that napping leads to Type 2 diabetes or any other health condition; many factors could be responsible for the results. In any observational study such as this one, there is no way to know whether researchers adjusted for all of the existing factors that could both lead someone to nap longer and raise his or her risk of prediabetes or diabetes. Any undetected and undiagnosed metabolic condition, for example, that led to both longer napping and a higher diabetes risk would be missed. When studying napping, however, it is virtually impossible to design a study that eliminates this possibility for error — most people cannot simply take a nap for as long as researchers tell them to, as would be needed for a randomized controlled trial on napping to be successful. Based on this study, though, it is conceivable that longer naps could disrupt sleep patterns and lead to metabolic changes that increase a person’s risk of developing prediabetes and Type 2 diabetes.
What do you think — could napping be hazardous to your health, or is it more likely that unhealthy people simply nap for longer periods? Have you ever noticed changes in your eating or exercise habits that seemed to follow changes in your sleep or napping patterns? Have you slept or napped more, or less, since you developed diabetes? Is there a right or wrong way to nap? Leave a comment below!