For most healthy adults, a short nap of 10 to 30 minutes in the early afternoon doesn’t hurt night sleep and can leave you more alert. Naps that are long, late in the day or taken most days are more likely to make it harder to fall asleep and leave your night more broken, and if you already have trouble sleeping at night, napping can make it worse.
Here’s why timing and length matter, what the research says, and how to check what naps do to your own nights.
Why a nap can affect the night
Two systems decide when you feel sleepy.
The first is sleep drive. From the moment you wake up, pressure to sleep builds, and it gets stronger every hour you’re awake. Part of this comes from adenosine, a by-product of your brain using energy, which builds up while you’re awake and makes you feel drowsy. The National Institute of Neurological Disorders and Stroke explains how this pressure is released when you sleep.
The second is your body clock, which makes you more alert at some times of day and sleepier at others. Many people feel a dip in the early afternoon, which is part of why naps are so tempting after lunch.
A nap releases some of that built-up sleep pressure. That’s why you feel better afterwards. But it also means you go to bed with less pressure than you would have had. A short nap early in the day takes off only a little, and you have hours to build it back. A long nap at 6 PM takes off a lot, close to bedtime, and you may lie awake at 11.
What the research says
A review of napping research found that how much a nap helps depends on its length, its timing, your age and whether you nap regularly. The same things decide how much it affects your night.
Timing matters most. In a 2022 study in the Journal of Sleep Research, 62 young adults wore activity trackers for eight days. Naps taken less than seven hours before night sleep went with worse nights than earlier naps, including taking longer to fall asleep and waking more often. Mayo Clinic advises napping before 3 PM, and Cleveland Clinic suggests before 2 or 3 PM.
Frequency matters too. In the same study, people who napped three or more times in eight days had more broken night sleep than those who napped once or twice, or not at all. The study was small and can’t show that naps caused the broken sleep. It may also work the other way: people who sleep badly at night may nap more.
Length matters for how you feel afterwards. Once a nap runs long, you’re more likely to wake from deep sleep, which leaves you groggy for a while. This is called sleep inertia.
- In a lab study in the journal Sleep, people who’d slept only about 5 hours took afternoon naps of different lengths. A 10-minute nap gave the quickest boost to alertness and mood. A 30-minute nap brought a spell of grogginess first, then benefits later.
- Mayo Clinic calls 20 to 30 minutes ideal. Cleveland Clinic suggests 15 to 20, and says naps over an hour bring more grogginess and more trouble sleeping at night.
In the 2022 study, nap length on its own wasn’t linked to worse nights. Only timing and how often people napped were. So a 40-minute nap at 1 PM is likely less of a problem for your night than a 20-minute one at 7 PM.
Who should be more careful
People with insomnia. If you struggle to fall asleep or stay asleep, Mayo Clinic notes that naps can make it worse. Holding on to that sleep drive until bedtime often helps.
People who need naps every day. Needing to nap often can be a sign you aren’t getting enough sleep at night, or of a sleep disorder such as narcolepsy. Cleveland Clinic says you shouldn’t be struggling to stay awake during the day.
For shift workers, though, the American Academy of Sleep Medicine recommends planned naps before or during a night shift to stay alert on the job.
How to check what naps do to your nights
Your own data can show you more than general advice.
Compare nights after naps with nights without. Over two or three weeks, look at how long you slept, how long it took to fall asleep and how often you woke (reading your sleep chart shows where to find each), on days you napped and days you didn’t.
Note when you napped, not just whether. If late naps line up with your restless nights and early ones don’t, that’s your answer.
Count naps and nights together. If your nights are short and you’re napping most afternoons, your total sleep may be fine but split in two. Moving more of it into the night is often the fix.
Know what your device records. Not every device records naps, and a short one can be missed. If a nap you know you took isn’t there, your watch may not have caught it.
This isn’t medical advice (see our health disclaimer). If you’re very sleepy during the day even after full nights, or you nod off when you don’t mean to, talk to a doctor.
How Voke shows naps
Voke picks one main night for each day and lists any other sleep that day as a nap, with its own start time and length. Naps show up as separate entries in your Feed and on the Sleep screen, next to the night rather than mixed into it, so they never change the night’s numbers or scores. If two devices record the same nap, Voke counts it once. You can read more about how Voke tells a nap from the night.
Sources
- National Institute of Neurological Disorders and Stroke: Brain basics: understanding sleep
- Mograss et al., Journal of Sleep Research, 2022: The effects of napping on night-time sleep in healthy young adults
- Brooks and Lack, Sleep, 2006: A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative?
- Milner and Cote, Journal of Sleep Research, 2009: Benefits of napping in healthy adults
- Mayo Clinic: Napping: do’s and don’ts for healthy adults
- American Academy of Sleep Medicine: Practice parameters for circadian rhythm sleep disorders, including shift work
- Cleveland Clinic: Are long naps bad for you?