A short nap gives your brain a quick reset. Even 10 to 20 minutes of light sleep in the early afternoon can make you more alert, sharpen your reaction time and lift your mood for a few hours, and a longer nap that includes deeper sleep can help you hold on to things you have just learned. The catch is timing and length: nap too long or too late and you may wake up groggy and sleep worse at night.
Napping has an image problem in many workplaces, where it can look like laziness. The research tells a more useful story. Below we look at what happens in the brain during a nap, what studies from NASA and elsewhere actually found, how nap length changes the effect, what the evidence says about naps and heart health, and who should probably skip them.
What happens in your brain during a nap
Sleep is not one state. Through the night we cycle roughly every 90 minutes through light sleep (stages N1 and N2), deep slow-wave sleep (N3) and REM sleep, when most vivid dreaming happens. A nap is a short slice of that cycle, and which stages it reaches decides what you get out of it.
In the first few minutes you drift into light sleep. Stage N2 is marked by bursts of brain activity called sleep spindles, which researchers link to strengthening newly learned skills and facts. If you stay asleep longer, you sink into slow-wave sleep, which helps consolidate memories and clears some of the "sleep pressure" that builds up during the day as a chemical called adenosine accumulates in the brain. Caffeine works partly by blocking adenosine's effects, which is why coffee masks tiredness rather than removing it.
Wake up during deep sleep and you are likely to feel thick-headed for a while. This is called sleep inertia. The Mayo Clinic notes it usually fades within about half an hour, but it is the main reason a long nap can leave you feeling worse before you feel better.
What the research has found
Humans are unusual among mammals in packing most of our sleep into one long block. Sleep researchers often cite estimates that the large majority of mammal species sleep in several shorter bouts, and it is still debated how much our single night of sleep reflects biology and how much reflects work schedules and artificial light. What is clear is that many adults do not get enough: the US Centers for Disease Control and Prevention has reported that about one in three American adults regularly sleeps less than the recommended seven hours.
NASA's cockpit nap study
The best-known nap experiment involved long-haul airline pilots. In research published by NASA scientists led by Mark Rosekind in the mid-1990s, crews on transpacific flights were given a planned 40-minute rest opportunity in the cockpit, one pilot at a time. Those who rested fell asleep quickly and slept for about 26 minutes on average. Compared with a no-rest group, they showed better vigilance later in the flight, with roughly 16 percent faster median reaction times and about a third fewer attention lapses, and fewer signs of micro-sleeps during the final descent. The findings helped shape "controlled rest" policies that some airlines and regulators now allow.
Naps versus coffee
A 2008 study led by Sara Mednick compared an afternoon nap, a dose of caffeine and a placebo. People who napped did better at recalling word lists and learning a motor skill than those who had caffeine, and caffeine actually hurt performance on some of the learning tasks. The naps in that study were long, 60 to 90 minutes, so they are not directly comparable with a quick power nap. A popular compromise, the "coffee nap", involves drinking coffee and then lying down for 15 to 20 minutes, waking just as the caffeine starts to act; small studies suggest it beats either one alone for alertness.
Naps and brain health
Research is also looking at long-term effects. A 2023 study in the journal Sleep Health, led by Valentina Paz with colleagues at University College London, used genetic data from tens of thousands of UK Biobank participants aged 40 to 69. People genetically inclined to nap regularly had slightly larger total brain volume, equivalent to around 2.6 to 6.5 years less brain ageing. The team had no information on nap length, and the result is about a modest average difference, not a promise for individuals.
Do naps protect the heart?
An often-repeated claim is that napping cuts your risk of dying from heart disease. It traces back mainly to a study of more than 23,000 Greek adults published in 2007 in the Archives of Internal Medicine by Androniki Naska, Dimitrios Trichopoulos and colleagues. Over about six years, people who took a siesta of 30 minutes or more at least three times a week had a 37 percent lower risk of dying from coronary heart disease than non-nappers, after allowing for other factors. The link was strongest among working men. The researchers suggested stress relief might explain it, and Trichopoulos cautioned that the findings needed confirmation before anyone changed work habits.
Since then the picture has become more mixed. Some later studies found that occasional short naps were linked with lower cardiovascular risk, while others found that regular naps of more than an hour were linked with higher risks of high blood pressure, diabetes and heart disease. The Mayo Clinic summarises the same pattern. One likely reason is that long daytime sleep can be a symptom of poor night-time sleep, sleep apnoea or illness, rather than a cause of problems.
The old idea that "siesta countries" have few heart attacks while the UK and US suffer because they shun naps does not hold up. Heart disease is a leading cause of death across Europe, including in Mediterranean countries, and national rates depend on diet, smoking, healthcare and many other factors. Napping may be one healthy habit among several, not a shield on its own.
How long should a nap be?
The right length depends on what you want from it. As a rough guide drawn from sleep researchers and clinical advice:
- 10 to 20 minutes: the classic power nap. You stay in light sleep, wake easily, and get a boost in alertness and energy that can last a couple of hours. For most people on a workday, this is the sweet spot.
- About 30 minutes: still helpful, but you are more likely to drift toward deep sleep and feel groggy for a short time after waking.
- About 60 minutes: more slow-wave sleep, which can help with remembering facts, places and faces, but sleep inertia is more likely.
- About 90 minutes: a full sleep cycle, including REM. Some studies link this with gains in creative problem-solving and learning, and because you wake at the end of a cycle you may feel less groggy than after 45 to 60 minutes. It takes a big bite out of the afternoon, though, and can make it harder to fall asleep at night.
The Mayo Clinic suggests keeping regular naps to around 20 to 30 minutes and taking them in the early afternoon, ideally before 3 p.m. That timing matches a natural dip in alertness many people feel after lunch, regardless of what they ate.
Tips for a better nap
- Set an alarm so a quick rest does not turn into a long sleep.
- Find a quiet, dim spot. An eye mask or earplugs help if you cannot control the room.
- Lie down or recline if possible; sitting fully upright makes it harder to fall asleep.
- Give yourself a few minutes after waking before driving or making important decisions.
- Do not worry if you only doze. Even lying quietly with your eyes closed can be restful, and light sleep counts.
When napping is not a good idea
Naps are not for everyone. If you have insomnia or struggle to fall asleep at night, daytime sleep can reduce the sleep drive you need at bedtime, and doctors often advise skipping naps while working on night-time sleep. Some people simply wake from any nap feeling dazed and find it hard to concentrate afterwards. And in some workplaces, a nap at your desk will not be welcome, however good the science.
Pay attention, too, if you suddenly need to nap much more than usual or still feel tired after a full night in bed. Persistent daytime sleepiness can be a sign of a sleep disorder such as sleep apnoea, a side effect of medication or another health problem. In that case, talk to a doctor rather than just scheduling more naps.
For most healthy adults, though, a short afternoon nap is a low-cost way to feel sharper. Keep it brief, keep it early, and treat it as a supplement to good night-time sleep rather than a replacement for it.
Sources: Mayo Clinic: Napping do's and don'ts for healthy adults; Harvard Gazette on the Greek siesta study (2007); NASA planned cockpit rest study (PubMed); Mednick et al., caffeine, naps and placebo (2008); UCL: Regular napping linked to larger brain volume (2023). Earlier version via Why Don't You Try This, Real Farmacy, Healthy Holistic Living and Care2.
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