Does daytime sleeping have a positive effect, or can naps be bad for people? For some, there's nothing quite as refreshing as a midday nap. According to the National Sleep Foundation (opens in new tab), a U.S. nonprofit organization, about one-third of American adults nap daily, while in some countries — such as Spain, Italy, Mexico and Greece — a quick afternoon siesta is a cultural tradition that dates back centuries. But is napping good for you? According to Moira Junge (opens in new tab), a registered health psychologist and CEO of the Sleep Health Foundation (opens in new tab), a nonprofit health promotion charity in Australia, there is nothing inherently wrong with taking a nap. However, she said that needing to sleep a lot during the day could be a sign that a person is not getting enough quality sleep at night. Most adults require between seven and nine hours of sleep per night, according to the National Sleep Foundation (opens in new tab). "If you require many naps during the day, despite adequate opportunity for sleep at night, this may be a sign that you're not getting enough sleep or that your quality of sleep is poor," Junge told Live Science. She recommended people take a short 20-minute nap if they feel the need for one, but also cautioned against long or multiple naps as they may interfere with the ability to get a longer sleep at night. “So, the simple answer is that short naps are natural, normal and often good for you,” she said. Hans Van Dongen (opens in new tab), the director of Washington State University's Sleep and Performance Research Center, agreed, but noted that napping could also be indicative of an underlying health issue. "If someone has ample opportunity for nighttime sleep yet finds that supplementing with a nap is necessary to maintain alertness and wellbeing, it can be a sign that their nighttime sleep is not sufficiently restorative," he told Live Science. "Seeking the advice of a doctor trained in sleep medicine to screen for potential disorders or medical conditions could be warranted." For instance, sleep apnea is a condition in which people experience pauses in breathing or shallow breathing during sleep. This can lead to daytime fatigue, making people more likely to seek out a midday snooze. It’s also worth noting that observational studies have found that people who nap more frequently, on top of sufficient nighttime sleep, have higher mortality in observational studies. One 2019 study, published in the European Heart Journal (opens in new tab), found that daytime napping is associated with increased risks of major cardiovascular events and deaths in those who get more than six hours of nighttime sleep, but not in those sleeping less than six hours per night. "If nighttime sleep is restricted for other reasons, [such as] an occasional disrupted night because of work, then napping is usually a good thing [and] can be restorative," Van Dongen said. However, too much sleep, it appears, can be detrimental. This is known as hypersomnia, a neurological disorder of excessive time spent sleeping or excessive sleepiness. What does napping do? Sleep, be it for long or short periods, provides a cooling off period for the brain, Junge said. "There is a change in the electrical activity of the brain waves and there may even be a flushing of toxins which can be seen during the longer sleep periods." A 2019 study published in the journal Science (opens in new tab) found that during sleep, the brain washes itself using a blend of cerebrospinal fluid — a clear, colorless fluid that flows in and around the brain and spinal cord — and blood. This process is thought to remove toxins and waste proteins that build up in the brain during the day, essentially refreshing the brain upon waking. Additionally, a 2021 study published in the International Journal of Environmental Research and Public Health (opens in new tab) found that taking a nap in the afternoon can improve cognitive performance and alertness for around two hours after the nap. In particular, naps taken in the early afternoon tend to be more effective when it comes to bolstering cognitive performance. How long should you nap for? While naps can be restorative, they can have different effects depending on why they are taken, according to Kevin Morgan (opens in new tab), emeritus professor of psychology at Loughborough University in England. When people aren’t necessarily feeling sleep deprived or fatigued, for example, a nap can still support wellbeing. Morgan called this an “appetitive nap”. A “compensatory nap”, on the other hand, when someone is sleep deprived, can help to re-calibrate levels of a molecule called adenosine. Lower adenosine levels promote alertness, while higher levels can promote sleepiness. Van Dongen also said that while some naps are beneficial, others can leave people feeling far from fresh. This is known as sleep inertia, a physiological state of impaired cognitive performance that can occur in the immediate aftermath of both nighttime sleep and naps. "Temporary grogginess, disorientation, and reduced alertness can follow after awakening from any sleep period, and takes a little while — typically around 15 minutes — to dissipate," Van Dongen said. "This is not usually an issue when people have time to let sleep inertia pass, but it can be problematic for people who are on call or otherwise need to be optimally alert immediately after awakening," which is often the case with people who nap. For individuals with chronic insomnia, Morgan said that sleep inertia can worsen symptoms and does not recommend they partake in daytime napping. For those without chronic insomnia, naps of under 30 minutes tend to be less likely to cause sleep inertia. When a person sleeps for over 30 minutes they are more likely to enter the deeper stages of sleep, Junge said. Like with sleep inertia, waking during these stages can also leave people feeling groggy, drowsy, disoriented and confused, so sleeping for 20 minutes or so, before 3 p.m., is ideal, Junge added. Any later may impact nighttime sleep. But "30 minutes or less" isn't a hard-and-fast rule. "In some cases, a longer nap of around 1.5 hours may also be beneficial," Junge said. "This length of time allows the body to cycle through the stages of sleep and avoids interrupting deep sleep. This type of longer nap may be especially helpful for emergency workers and shift workers who are trying to avoid fatigue and have to cope with a reduced opportunity for adequate sleep." Source
