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In some countries, napping is quite common. It’s supposed to be healthy and make people more productive – but several studies contradict that, finding a link between naps and a higher risk of high blood pressure and stroke. It may even be an early signal of dementia, they say.
While the siesta is a tradition in Japan and Spain and is becoming increasingly popular in Silicon Valley, napping is less common in this country – at least in the workplace. Yet napping during the day is good for concentration, creativity and productivity. But some studies have shaken the positive image.
Those who regularly take a short nap during the day increase their risk of high blood pressure and stroke: with this observation, a study published in the journal “Hypertension” recently shocked lovers of napping. Using data from the United Kingdom, the Chinese authors reported that frequent or regular daytime naps were associated with a 12 percent higher risk of developing hypertension and a 24 percent higher risk of stroke in adults – compared with people who never napped.
This included a high percentage of men among regular daytime nappers, as well as participants with low levels of education and income and people who smoked, drank alcohol daily, suffered from insomnia or were more likely to be night owls.
Daily naps are warning signs of Alzheimer’s disease
Sleep researcher Michael Grandner of the University of Arizona stresses in a commentary probably not the rest itself is harmful. Rather, he says, many people who take short naps during the day do so because of a lack of sleep at night: “Poor nighttime sleep is associated with poorer health, and a nap is not enough to compensate.”
Thus, the research confirms previous findings that “more naps seem to reflect an increased risk of heart health problems and other issues.” In addition, a recent study found that increasing naps could be an early signal of dementia – especially when adequate nighttime sleep exists.
Naps can fire creativity.
However, that’s no reason to demonize napping in general. A French study found that it could boost creativity in a very short form. Greek researchers also observed that a half-hour nap could even protect against cardiovascular disease – but only if you take it no more than once or twice a week, a Swiss study added.
In addition, younger people seem to benefit from napping during the day. A U.S. study showed that naps positively affect teenagers’ concentration and learning behaviour. This is due not least to the fact that they often have a shifted sleep rhythm: they go to bed late but have to get up early for school.
However, napping is often frowned upon in many Western countries, says lead author Xiaopeng Ji of the University of Delaware. The monophasic sleep pattern (i.e., only one sleep phase without additional naps) would be considered a sign of mental maturity. In China, however, it’s different, he said, where “nap time is integrated into the schedule after lunch for many adults at work and for students at school.” In other countries, such as Japan and Spain, horizontal nap time is also part of the work culture.
Miracle effects should not be expected from a nap, as a Michigan State University study suggests: As its authors write in the journal Sleep, a short rest has little benefit for cognitive abilities and, most importantly, would not make up for a night of poor sleep. “We found that short naps of 30 or 60 minutes had no measurable effects,” lead author Kimberly Fenn summarizes.
Midday naps important for three types
Regardless of what an afternoon nap does, the need for it appears to be partly genetic. At least, that’s what sleep physicians at Massachusetts General Hospital found in a major study. As they report in the journal “Nature Communications,” there are three types for whom a nap is particularly important: first, people who get up very early, and second, those who suffer from sleep disorders. A short sleep break during the day is necessary to recharge the batteries.
Third, he said that some people need more sleep for genetic reasons and, therefore, like to take short naps during the day. “This shows us that napping during the day is biologically determined and not just an environmental or behavioral choice,” says co-author Hassan Saeed Dashti.
However, health problems such as high blood pressure or pronounced obesity could lead to above-average fatigue. More research on the causes is needed here, which could also focus more on individual rest needs, says physiologist Marta Garaulet, another co-author. “Future work could help develop personalized recommendations for siesta.”
Are you still working or already asleep?
Previous studies on the topic suggest that the optimal length of a midday nap and whether it is necessary depends primarily on individual factors. People who suffer from sleep disorders at night should refrain from napping, as they might otherwise get tired even later in the evening.
With this in mind, one should also not allow oneself a nap too late in the day and not rest for too long: 20 to 30 minutes seem ideal to avoid slipping into REM sleep and feeling even more shattered after waking up than before.
And according to Australian researchers, the refreshing effect of the optimal nap could be enhanced by a surprising trick: If you drink a coffee before napping and set your alarm clock for 20 minutes, you’ll wake up with just the caffeine boost.
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