While some evidence has suggested that a daily afternoon nap is likely to boost productivity and health, taking that nap a bit too far could put your health at risk.
According to a recent study conducted at the University of Tokyo, taking long afternoon naps could be a warning sign of metabolic syndrome, which is a combination of diabetes, high blood pressure and obesity.
The researchers gathered about 200 other studies and did a meta-analysis of the data for a group of over 261 000 people. All these studies used self-reporting to determine daytime sleepiness and napping habits of the participants. They were asked questions like: “Do you have a problem with sleeping during the daytime?”. Their answers were analysed in conjunction with their family history of type 2 diabetes and obesity.
It was found that taking a regular daytime naps that lasted longer than an hour increased the risk of developing type 2 diabetes by 46%. Shorter naps on the other hand did not affect diabetes risk at all.
“Several studies have demonstrated the beneficial effects of taking short naps less than 30 minutes in duration, which help to increase alertness and motor skills. A short nap finishes before the onset of deep slow-wave sleep,” said Dr Tomohide Yamada, leader of the study. “Entering deep slow-wave sleep and then failing to complete the normal sleep cycle can result in a phenomenon known as sleep inertia, in which a person feels groggy, disoriented, and even sleepier than before napping,” he continued.
The researchers were, however, unsure of whether the problem was the napping itself, or if another factor was causing people to be sleepy during the day.
“Daytime napping might be a consequence of night-time sleep disturbance such as obstructive sleep apnoea. Epidemiological studies have shown that obstructive sleep apnoea is independently linked to blockages (ischaemia) of heart arteries, stroke, fatal and non-fatal cardiovascular events, and all-cause mortality,” said Yamada.
According to the International Diabetes Federation Africa, there are about 2,28 million cases of diabetes in South Africa, and the figure is continuing to rise.
Dr Yamada concluded that clarifying the relationship between naps and metabolic disease could offer a new strategy for the treatment of the disease.