While in Japan and Spain the siesta is an integral part of the work culture and is also becoming increasingly popular in Silicon Valley, napping is less common here - at least in the workplace. A nap during the day is considered good for concentration, creativity and productivity. But some studies have shaken the positive image.
Anyone who regularly takes a short nap during the day increases their risk of high blood pressure and stroke: a study recently published in the specialist journal "Hypertension" shocked nap lovers with this observation. Using data from the UK, the Chinese authors reported that frequent or regular daytime naps were associated with a 12 percent higher risk of developing high blood pressure and a 24 percent higher risk of stroke in adults, compared to people who didn't never took a nap.
There was a high percentage of men among the regular day sleepers, as well as participants with a low level of education and income, and people who smoked, drank alcohol daily, suffered from insomnia or were more likely to be nocturnal.
Sleep researcher Michael Grandner from the University of Arizona emphasizes in a comment that the nap itself is probably not harmful. Rather, many people who nap briefly during the day would do so at night due to lack of sleep: "Poor night's sleep is associated with poorer health, and a nap is not enough to compensate."
The study confirms previous study findings that "more naps appear to reflect an increased risk of heart health and other problems." In addition, a recent study showed that increasing naps could be an early sign of dementia - especially if you actually get enough sleep at night.
That's no reason to demonize naps in general, though. A French study found that this could increase creativity in a very short time. Greek researchers also observed that a half-hour nap could even protect against cardiovascular disease - but only if you don't take it more than once or twice a week, as a Swiss study added.
In addition, younger people in particular seem to benefit from a nap during the day. A US study showed that this has a positive effect on concentration and learning behavior in teenagers. This is not least due to the fact that they often have a shifted sleep pattern: They go to bed late but have to get up early because of school.
One should not expect miracle effects from a nap, as a study by Michigan State University suggests: As the authors write in the journal "Sleep", a short nap has little benefit for cognitive abilities and, above all, would not compensate for a bad night's sleep. "We found that short naps of 30 or 60 minutes had no measurable effect," summarizes lead author Kimberly Fenn.
Regardless of what a nap does, the need for it seems in part genetic. At least that's what sleep physicians at Massachusetts General Hospital found in a large study. As they report in the journal Nature Communications, there are three types for whom a nap is particularly important: on the one hand, people who get up very early, and on the other hand, those who suffer from sleep disorders. For both of them, the short sleep break during the day is necessary to recharge the batteries.
Thirdly, there are also people who, for genetic reasons, need more sleep and therefore like to lie down briefly during the day. "This tells us that daytime naps are biological, and not just an environmental or behavioral choice," says co-author Hassan Saeed Dashti.
However, health problems such as high blood pressure or being overweight could also lead to above-average tiredness. According to physiologist Marta Garaulet, another co-author, further investigations into the causes are needed here, which could also place a stronger focus on individual rest needs. "Future work could help develop personalized siesta recommendations."
In fact, previous studies on the subject suggest that the optimal length of a nap and whether it is necessary at all depends primarily on individual factors. Especially people who suffer from insomnia at night should avoid naps, otherwise they could get tired later in the evening.
With this in mind, you shouldn't take a nap too late in the day and don't rest too long: 20 to 30 minutes seems ideal to avoid slipping into REM sleep and waking up feeling even more exhausted than before.
And, according to Australian researchers, the refreshing effect of the optimal nap could be increased with a surprising trick: If you drink a coffee before your nap and set your alarm clock for 20 minutes, you'll wake up with the caffeine boost.