The Science of Power Naps: How Long is Too Long?

It’s 3 pm, lunch is settling, and your eyelids feel heavy. A short nap can be one of the simplest ways to get through that slump. But anyone who has “just closed their eyes for a bit” and woken up an hour later, foggy and grumpy, knows that naps can backfire.

The difference comes down mostly to length and timing. Here’s what the research says about how long to nap, when to do it, and when frequent long naps may be a sign of something worth checking.

At a glance

• Aim for 10–20 minutes. Short naps boost alertness with little grogginess afterwards. In one lab study, a 10-minute nap gave the quickest benefit.
• Nap in the early afternoon. Napping after about 3 pm can make it harder to sleep at night.
• Longer isn’t better. Naps of 30 minutes or more are more likely to leave you groggy (“sleep inertia”) for a while after waking.
• Regular naps over an hour are linked with health risks. Large reviews link them with higher rates of heart disease, metabolic problems and early death, although they don’t prove that the naps are the cause.
• Naps don’t replace night-time sleep. If you need a nap every day, look at your night-time sleep first.
• Feeling very sleepy despite a full night’s sleep? Speak to a doctor. It can be a sign of a sleep disorder such as sleep apnoea.

What happens in your brain when you nap

Why you feel sleepy in the afternoon

That early-afternoon slump isn’t only about a heavy lunch. Your body clock has a natural dip in alertness around 1–3 pm, and it’s stronger if you slept badly the night before. A very large lunch may add to the drowsiness, and many people find a lighter, balanced lunch keeps them more alert.

Sleep happens in stages

When you fall asleep, your brain moves through different stages of sleep:

• Light sleep (N1 and N2): the first few minutes are very light sleep, followed by stage 2, which typically lasts 10–25 minutes. Waking from these stages is fairly easy.
• Deep sleep (N3): this follows, and it’s much harder to wake from.
• REM sleep: the dreaming stage, which usually comes later.

A full cycle through these stages takes about 90 minutes on average.

Why length matters: sleep inertia

Wake up during deep sleep and you’re likely to feel groggy, slow and disoriented for a while. This is called sleep inertia. According to the Mayo Clinic, it usually wears off within about 35 minutes, but that’s long enough to spoil the point of a nap if you have a meeting or need to drive.

That’s the whole logic of the power nap: sleep long enough to get the benefit of light sleep, but wake up before you sink into deep sleep.

How long should a power nap be?

One of the best-known studies on nap length comes from Flinders University in Australia. Researchers restricted 24 healthy young adults to about five hours’ sleep, then compared afternoon naps of 5, 10, 20 and 30 minutes. As one summary of the study reports:

• 5 minutes gave few benefits compared with no nap.
• 10 minutes gave immediate improvements in alertness and performance, with some benefits lasting up to about 155 minutes.
• 20 minutes also helped, but the improvements only showed up about 35 minutes after waking.
• 30 minutes caused a period of grogginess and poorer performance straight after waking, before the benefits kicked in.

The researchers concluded that the 10-minute nap was the most effective of the lengths they tested. Most health organisations suggest a similar window: the Mayo Clinic describes 20–30 minutes as ideal, noting that longer naps are more likely to leave you groggy.

Nap lengths compared

Nap length	What to expect	Best for
10–20 minutes	Mostly light sleep; quick boost in alertness with little or no grogginess	A workday slump, before driving (after pulling over safely), studying
30–60 minutes	More likely to reach deep sleep; often groggy for a while after waking	Rarely ideal; leave time to wake up properly before anything demanding
About 90 minutes	Roughly one full sleep cycle, so you may wake from lighter sleep; more likely to affect night-time sleep	Occasionally, when you’re seriously short of sleep, such as before a night shift
Regularly over 60 minutes	Linked in studies with higher health risks (see below)	Worth discussing with a doctor if it’s a daily need

These are general guides. Some people wake refreshed after 30 minutes; others feel foggy after 15. Notice what works for you, and keep it short if you’re unsure.

The benefits of a short nap

A well-timed short nap won’t make up for weeks of poor sleep, but it can help in the moment. According to the Mayo Clinic, naps can:

• reduce tiredness and improve alertness
• lift your mood and help you relax
• support performance, including reaction time and memory

What the research shows

• Alertness on the job: in a well-known NASA study in the 1990s, long-haul pilots who were allowed a planned nap in the cockpit while colleagues flew showed up to 54% better alertness and up to 34% better job performance than pilots who didn’t nap. The pilots had a 40-minute rest opportunity, and the naps behind these results lasted about 26 minutes. These are best-case figures from a specific setting, but they show why some workplaces build in planned rest.
• Sleepy driving: in a driving-simulator study at Loughborough University in the UK, sleepy drivers who had caffeine followed by a 15-minute nap had far fewer sleep-related incidents than with caffeine alone, even when they didn’t fully fall asleep. If you feel drowsy while driving, the safest choice is always to stop somewhere safe and rest.
• Brain health: a 2023 UK Biobank study from University College London found that people genetically more likely to nap habitually had slightly larger total brain volume. The effect was modest and needs confirming, and the study didn’t look at nap length, so it isn’t a reason to start napping if you don’t need to.

What about a “coffee nap”?

Caffeine takes a little while to kick in, so some people drink a cup of coffee or tea and then nap for 15–20 minutes, aiming to wake just as it starts working. The driving study above suggests the combination can work well for sleepy people. If you try it, keep it to the early afternoon so the caffeine doesn’t disturb your night-time sleep, and skip it if caffeine makes you jittery or you’ve been advised to limit it.

How long is too long? When naps may be a warning sign

Short naps appear harmless for most people. Long, regular naps are a different story.

• A 2020 analysis presented at the European Society of Cardiology Congress pooled more than 20 studies with over 313,000 people. Naps longer than 60 minutes were linked with a 30% higher risk of death from any cause and a 34% higher risk of cardiovascular disease compared with not napping. Naps under an hour weren’t linked with heart disease.
• An earlier analysis of 21 studies and over 307,000 people from Asia and the West found a J-shaped link between nap length and metabolic syndrome: no increased risk below about 40 minutes, but rising risk with longer naps.

These studies show associations, not cause and effect. Long daytime naps may simply be a marker of something else going on, such as poor night-time sleep, an undiagnosed sleep disorder, depression or another health condition. That’s exactly why they’re worth paying attention to.

Naps and night-time sleep

Short naps rarely affect night-time sleep. But long or late naps can make it harder to fall asleep at night, especially if you already have insomnia. The NHS advises people with insomnia to avoid napping during the day. If you struggle to sleep at night, try cutting out daytime naps for a couple of weeks and see whether your night-time sleep improves.

When to see a doctor

Speak to your doctor if:

• you need to nap more than usual, or feel sleepy during the day even after a full night’s sleep
• you snore loudly, or someone has noticed your breathing stop and start or you gasp or choke during sleep. These are signs of sleep apnoea, which also causes daytime tiredness, poor concentration and morning headaches
• you fall asleep at unexpected times, such as during conversations or at the wheel
• daytime sleepiness started after beginning a new medicine

Untreated sleep apnoea and excessive sleepiness increase the risk of accidents, including on the road, so it’s worth getting checked rather than relying on naps to cope.

How to take a better power nap

1. Time it right. Aim for early afternoon, roughly between 1 pm and 3 pm, when your natural dip in alertness happens. The Mayo Clinic notes that napping after 3 pm can get in the way of night-time sleep.
2. Set an alarm. Most people take a few minutes to drop off, so set an alarm for about 20 minutes to get 10–20 minutes of actual sleep.
3. Make it easy to switch off. A quiet, dark, comfortably cool spot helps. At work, an eye mask, earplugs or noise-cancelling headphones can turn a reclined chair into a nap spot.
4. Don’t worry if you don’t fall asleep. Simply lying still with your eyes closed for 10–15 minutes can still feel restful.
5. Wake up properly before anything demanding. Give yourself a few minutes to get moving: stand up, splash water on your face, step into daylight or take a short walk. Avoid driving or any task needing quick reactions until you feel fully alert.
6. Watch the caffeine clock. If you have tea or coffee with your nap, keep it to the early afternoon. The NHS advises avoiding tea and coffee for at least six hours before bed.
7. Mind your lunch. A balanced, not-too-heavy lunch can make the afternoon slump easier to manage. Our meal-prep guide has lunch ideas that keep you going through the afternoon.

If you work shifts

Shift work disrupts your body clock, and planned naps can help. A nap before a night shift, or a short nap during a break if your workplace allows it, can improve alertness. If you’re very sleepy after a night shift, consider a short nap or other transport before driving home.

If you don’t nap at all

That’s fine. Napping isn’t essential if you sleep well at night and feel alert during the day, and the studies above give no reason for non-nappers to start. Some people simply can’t sleep during the day, and that’s normal too.

The bottom line

For most people, the best power nap is short and early: 10–20 minutes, sometime between lunch and 3 pm. That’s enough to sharpen your focus and lift your mood without leaving you groggy or stealing your night-time sleep. Long naps are a different matter. If you regularly need an hour or more in the day, treat it as a signal to look at your night-time sleep, and to talk to a doctor if the tiredness doesn’t add up.

Pro Tip: Use the GOQii App to track your sleep and see how naps, caffeine and bedtimes affect your nights. Your GOQii Personalised Health Coach can help you build a sleep routine that keeps you alert through the day, with or without a nap.

Frequently asked questions

How long should a power nap be?

For most adults, 10–20 minutes of sleep is ideal. In one study, a 10-minute nap gave immediate improvements in alertness that lasted up to about two and a half hours. Longer naps are more likely to leave you feeling groggy.

Is a 1-hour nap too long?

Occasionally, it’s fine if you’re very short of sleep, but expect to feel groggy for a while afterwards. Regular naps of an hour or more have been linked in studies with higher risks of heart disease and metabolic problems, so if you need long naps often, check your night-time sleep and speak to a doctor.

What is the best time to take a nap?

Early afternoon, roughly between 1 pm and 3 pm, when alertness naturally dips. Napping after 3 pm can make it harder to fall asleep at night.

Why do I feel worse after a nap?

You probably woke from deep sleep, which causes “sleep inertia”: grogginess that usually passes within about 35 minutes. Keeping naps under 20 minutes helps you wake from lighter sleep.

Do naps make up for lost sleep at night?

Only partly. A short nap can improve alertness for a few hours, but it doesn’t replace a full night’s sleep. Most adults need 7 or more hours of sleep a night.

Does a coffee nap work?

It can. In a driving-simulator study, sleepy drivers who had caffeine followed by a 15-minute nap had far fewer sleep-related incidents than with caffeine alone. Keep it to the early afternoon so the caffeine doesn’t affect your night-time sleep.

Is it bad to need a nap every day?

Not necessarily. Many people enjoy a short daily nap. But if you feel very sleepy every day despite sleeping 7–9 hours, snore loudly or fall asleep at unexpected times, speak to a doctor, as this can be a sign of a sleep disorder such as sleep apnoea.

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Disclaimer: The information provided in this blog is for general awareness and educational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for personalised medical guidance or concerns related to your health.