Biphasic Sleep: Does Splitting Your Sleep in Two Actually Work?

Biphasic sleep means sleeping in two blocks in a day instead of one, usually a main night sleep plus an afternoon nap. It's how people in siesta cultures have long slept, and it's popping up online as a "hack" for getting more done. This guide covers what biphasic sleep is, the common schedules, what the evidence says, how it differs from polyphasic sleep, who it may suit, and how to try it sensibly.

The short answer: biphasic sleep is fine if your total sleep still adds up to what you need, roughly seven to nine hours for most adults. A night sleep plus a nap is a normal human pattern, and short afternoon naps can improve alertness. What doesn't work is using split sleep to need less sleep overall: the evidence says you can't cheat your sleep need that way. If you try it, keep the nap early in the afternoon, keep your main sleep long, and stop if you feel worse.

What biphasic sleep is

Most adults in Australia sleep monophasically, in one block at night. Biphasic sleep splits the day's sleep into two blocks. A recent review in the journal Sleep notes that most humans live on a one-block schedule, but in siesta cultures a biphasic pattern is normal. It also mentions historical accounts of two separate night-time sleeps (source).

If you wake in the small hours, that history is a reminder that waking once in the night isn't automatically a problem. See why do I wake up at 3am for more on that.

Common biphasic schedules

Schedule	How it looks	Who it suits
Siesta	Six to seven hours at night plus a 60 to 90 minute afternoon sleep	People with a flexible afternoon, hot climates
Short nap	Seven-ish hours at night plus a 15 to 30 minute nap around 2pm to 3pm	Most adults who want a lift without disruption
Segmented night	Two night-time sleeps with an hour or so awake between	Rarely chosen. More often something people notice they already do
Shift split	Main sleep after a night shift plus a nap before the next one	Shift workers fitting sleep around a roster

The short nap version is the easiest to live with and the least likely to upset your night sleep.

What the evidence says

There isn't a big body of research on biphasic sleep as a lifestyle, but a few findings are useful.

Napping in the early afternoon works with your body clock. The Sleep Health Foundation notes that we often feel sleepiest around 2pm to 3pm, which makes napping easier then. It suggests 15 to 30 minutes to improve alertness and concentration, and warns that long naps can leave you groggy (source).

Splitting sleep can feel better, but has trade-offs. In a Singapore study, teenagers on restricted sleep were given either 6.5 hours in one block or 5 hours at night plus a 1.5-hour afternoon nap, over several nights. The split group had fewer attention lapses, better working memory and better mood, even though they slept slightly less in total. But their blood glucose rose more after a sugar drink test, and both restricted groups did worse than teenagers getting nine hours in bed. The researchers' conclusion was that young people are still best off getting the recommended amount of night sleep (source).

So a split schedule may be a reasonable way to arrange the sleep you have. It isn't a substitute for enough sleep.

Biphasic versus polyphasic sleep

Polyphasic schedules split sleep into many short naps across the day, often with the aim of sleeping far less. The Sleep review is blunt about this. Polyphasic sleepers had lower sleep efficiency and more light sleep compared with people simply sleeping short in one block. Every extra sleep–wake transition carries a cost: time to wind down and time to shake off grogginess. The review cites the US National Sleep Foundation's position that there is no evidence of benefit from polyphasic sleep and there are concerns about health risks and daytime functioning (source).

Biphasic sleep with enough total sleep is a normal pattern. Cutting sleep with lots of micro-naps is not.

Who it may suit, and who should skip it

May suit:

• Shift workers, who often need a main sleep plus a nap before a night shift.
• Parents of young children, where a nap while the baby sleeps fills a gap.
• People with a flexible afternoon who feel a strong post-lunch dip.

Probably skip it if:

• You have insomnia. Napping can take the edge off your sleep drive at night. See insomnia: what helps.
• You drive or operate machinery straight after naps, because of grogginess.
• You're trying to sleep less overall. It won't work.

How to try it sensibly

1. Work out your total first. Most adults need about seven to nine hours. See how much sleep do I need.
2. Keep the main sleep at night and make the nap the smaller block.
3. Nap early in the afternoon, not in the evening, so it doesn't push your bedtime back.
4. Choose short or full-cycle naps. 15 to 30 minutes avoids deep sleep. A longer nap of around 90 minutes covers a full cycle. See sleep cycles explained.
5. Always set an alarm for the nap. An unplanned two-hour nap is where biphasic sleep goes wrong.
6. Give it two weeks and be fair about how you feel. If you're groggier, sleep worse at night or need more caffeine, go back to one block.

Grogginess after a nap is normal for a few minutes. If it hangs around, read what is sleep inertia.

When to see your GP

If you need a nap every day just to function, even after a full night in bed, that's worth checking. Daytime sleepiness can be a sign of sleep apnoea or another sleep problem. This guide is general information, not medical advice.

Where the Sovune Nudge fits

We make the Sovune Nudge, a silent vibrating wristband alarm, so we're not neutral. Biphasic sleep lives or dies on the nap alarm, and that's where the Nudge is useful.

• Three separate alarms, so your nap alarm and your morning alarm are both set and ready.
• Silent vibration on your wrist, so you can nap at work, on the couch or next to a sleeping partner without disturbing anyone.
• Starts as a gentle tap and builds through three intensity levels, over a full minute, and you can switch it off sooner.
• Set on the band itself. No app, no phone, so you're not tempted to scroll before your nap.

It comes with a 30-day money-back guarantee.

Quick answers

Is biphasic sleep healthy? It can be, as long as your total sleep is enough. A night sleep plus a short afternoon nap is a normal pattern in many cultures.

Can biphasic sleep help me sleep less? No. Splitting sleep doesn't reduce how much you need, and cutting total sleep has costs either way.

How long should the second sleep be? Either a short nap of 15 to 30 minutes or a full cycle of around 90 minutes. Anything in between is more likely to leave you groggy.

Is waking in the middle of the night biphasic sleep? Sometimes it's just a normal brief waking. If you're awake for long periods most nights, talk to your GP.

For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.

See the Sovune Nudge →