Biphasic Sleep: Is Sleeping Twice a Day Healthy?

Can't seem to get a full eight hours of sleep at night? Splitting your sleep into two periods might be an option worth exploring.

Biphasic sleep means dividing your sleep into two separate chunks within a 24-hour period. You might already be doing this without realizing it has a name. Perhaps you go to bed at 10 PM, sleep until 2 AM, spend an hour reading, then go back to sleep until morning. Or maybe you take an afternoon nap and sleep less at night.

This sleep pattern has been around for centuries. Before electric lights became widespread, people commonly slept in two distinct phases.

But the real question is whether this approach benefits your health today.

The history of two-phase sleep

Historian A. Roger Ekirch discovered over 2,000 references to "first sleep" and "second sleep" in historical documents—everything from diaries and court records to Chaucer's Canterbury Tales and Homer's Odyssey [1].

The pattern was remarkably consistent. People would go to bed after sunset, sleep for four to five hours, wake around midnight, stay awake for an hour or two, then sleep again until dawn. During that wakeful period, they prayed, talked with family, did household chores, or read by candlelight.

This wasn't limited to Europe. The pattern appeared across the Middle East, Africa, Asia, Australia, and Latin America.

The Industrial Revolution changed everything. Gas lamps and electric lights extended the workday. Factory schedules required everyone to show up at the same time, making flexible sleep impractical. By the late 1800s, the two-phase pattern faded, and one continuous block of sleep became the norm.

In the early 1990s, psychiatrist Thomas Wehr at the National Institute of Mental Health tested what happens when you limit artificial light. He placed eight men in an environment with only 10 hours of light per day instead of the typical 16 hours [2]. 

By the fourth week, they naturally fell into a biphasic pattern—sleeping for three to five hours, waking for one to three hours, then sleeping another three to five hours. Lab tests showed their bodies had adjusted at a biological level.

What is biphasic sleep?

Biphasic sleep is a sleep pattern that involves two separate sleep periods within 24 hours. Most of us today follow monophasic sleep, getting all our sleep in one nighttime block.

There are three main types of people practicing Biphasic sleep today.

Segmented sleep

You go to bed early, sleep for several hours, wake up for a period, and then sleep again. Total sleep should still reach 7 to 9 hours. The wakeful period typically lasts one to three hours. In Wehr's research, people described these middle hours as unusually calm and peaceful rather than anxious [2].

Siesta sleep schedule

This pairs a 60 to 90-minute daytime nap with 5 to 6 hours of nighttime sleep. Mediterranean countries like Spain, Italy, and Greece have practiced this for generations. Businesses close during the hottest afternoon hours for rest.

The timing works with your body. Most people experience a natural dip in alertness between noon and 3 PM, regardless of lunch.

Short nap schedule

This combines 6 to 7 hours of nighttime sleep with a brief 20 to 30-minute afternoon nap. The short duration helps you avoid grogginess while still providing mental refreshment.

Benefits of biphasic sleep

Research shows several potential benefits, particularly for patterns that include afternoon naps.

Sharper thinking and better memory

Multiple studies show that midday naps improve cognitive performance. A 2021 analysis found improvements in alertness, memory recall, and problem-solving. The benefits were strongest when naps happened before 1 PM and when people tested their abilities 60 to 120 minutes after waking [3].

Researchers at UC Berkeley studied 39 adults. Half took 90-minute naps at 2 PM, while the other half stayed awake. By 6 PM, the nappers showed clear improvement in learning new information, while the non-nappers got worse as the day went on [4].

Research on preschool children supports this. Kids who napped after learning new information retained significantly more knowledge both right after the nap and 24 hours later. Kids who stayed awake showed substantial forgetting [5].

Heart health protection

A Greek study followed 23,681 healthy adults for several years, looking at napping habits and heart health. The results were significant:

• People who napped occasionally (less than 3 times weekly) had 12% lower coronary mortality

• People who napped regularly (3 or more times weekly) had 37% lower coronary mortality

• The effect was most pronounced among working men

Researchers believe napping reduces stress and lowers activity in the sympathetic nervous system. Chronic stress contributes to high blood pressure and heart attacks. The midday rest period gives your cardiovascular system a break [5].

Nap duration matters, though. Very short naps (under 30 minutes) and very long naps (over 90 minutes) didn't show the same benefits. Moderate-length siestas appeared most protective.

More energy during the day

Taking a strategic nap during the afternoon slump can reduce daytime sleepiness. The National Sleep Foundation reports different effects based on length:

• Short naps (20-30 minutes) boost alertness without grogginess

• Longer naps (60-90 minutes) allow for a complete sleep cycle and deeper restoration

Athletes have paid attention to this. A 2024 review found that afternoon sleep periods improve reaction time, endurance, and sport-specific skills [6]. Professional sports teams now include strategic napping in training schedules.

Less stress

Short naps help regulate your stress response. During a nap or quiet rest period, several things happen:

• Sympathetic nervous system activity decreases

• Blood pressure and heart rate decline

• Stress hormones normalize

The psychological benefit matters too. Stepping away from work demands gives your mind time to recover.

Also Read: Tired of Feeling Tired? How Sleep Makes You More Productive

Downsides of biphasic sleep

Biphasic sleep has some potential drawbacks to consider.

You might not get enough deep sleep

Sleep isn't the same throughout the night. You cycle through different stages—light sleep, slow-wave sleep (deep sleep), and REM sleep. Each serves specific functions, from physical restoration to memory processing.

When sleep is divided, cycling through these stages may become less efficient. A 2021 study found that people who split their sleep sometimes got less slow-wave sleep compared to those who slept continuously, especially when sleep segments were too short to complete full 90-minute cycles [7].

Your body needs deep sleep for physical recovery and immune function. REM sleep supports emotional regulation and memory. Fragmenting sleep into very short periods may reduce time in these restorative stages.

It can mess with your schedule

Unless you have flexible hours, finding time for a substantial midday nap is difficult. Most workplaces don't provide nap spaces, and stepping away for an hour isn't feasible for many jobs.

Family and social obligations add complexity. Evening plans, morning responsibilities, and children's schedules may all conflict with your intended sleep times.

Grogginess after naps

Waking from deep sleep can cause grogginess that lasts from a few minutes to half an hour. This phenomenon, called sleep inertia, can be problematic if you need to resume demanding tasks right away.

Nap length affects how you feel:

• Under 30 minutes - Lower grogginess risk

• 30-60 minutes - Highest grogginess risk

• 90 minutes - Completes full cycle, reduces grogginess

It could mean sleep problems

If you can't function without splitting your sleep, or if you feel constantly exhausted despite adequate total sleep, an underlying issue might exist.

Sleep apnea, insomnia, or delayed sleep phase syndrome requires proper medical diagnosis and treatment. Schedule adjustments won't address these disorders and might delay necessary help.

Your total sleep still needs to add up

The biggest risk is not getting enough total sleep. Adults need at least 7 hours for optimal health, with most people functioning best on 7 to 9 hours.

If you sleep only 5 hours at night plus a 30-minute nap, you're getting 5.5 hours total. That's insufficient regardless of how you divide it. Chronic sleep deprivation leads to serious consequences:

• Increased risk of heart disease and stroke

• Higher rates of diabetes and obesity

• Impaired immune system

• Memory problems and difficulty concentrating

• Elevated risk of depression and anxiety

• Cognitive decline in older adults

Studies show that regularly sleeping less than 6 hours per night is linked to a significantly higher risk of heart attack over time compared to getting at least 7 hours. 

Also Read: Sleep Debt: What Does It Really Mean for Your Well-Being?

Who might benefit from biphasic sleep?

Certain situations lend themselves better to split sleep schedules.

People with non-traditional work hours often struggle with conventional sleep patterns. Those working night shifts or unusual hours may find that dividing sleep helps them meet both work and rest requirements.

Those in siesta cultures have built-in support. When businesses close during midday and rest is culturally expected, maintaining a biphasic schedule becomes much easier.

Parents with young children face interrupted nighttime sleep regardless of planning. Adding a strategic nap when the baby sleeps can help reach total sleep requirements.

Students learning new information may benefit from the memory consolidation that occurs during naps. Research shows that napping after studying helps the brain process and retain new information more effectively.

People with flexible schedules can experiment more easily. Remote workers, freelancers, and self-employed individuals have the freedom to structure their days around biphasic sleep.

Older adults tend to experience more fragmented sleep with age. Many wake during the night and worry that something is wrong. Understanding that some nighttime waking can be normal may reduce anxiety and make falling back asleep easier.

Who should avoid biphasic sleep?

Some situations make biphasic sleep less appropriate.

People with insomnia face particular challenges. Adding more sleep transitions creates additional opportunities for problems. Healthcare providers often recommend that insomnia patients avoid daytime napping to build sleep pressure for nighttime.

Those who get very groggy after naps may find that sleep inertia outweighs any benefits. If you already struggle with morning waking, adding a midday wake-up could make things worse.

Anyone with a diagnosed sleep disorder should consult a doctor before changing sleep patterns. Sleep apnea, narcolepsy, and restless leg syndrome require specific treatments that schedule changes could disrupt.

People with unpredictable schedules will struggle. Your body needs regularity to adapt to any sleep routine. If work shifts change frequently or daily routines vary substantially, the inconsistency prevents proper adjustment.

Also Read: Debunking Common Sleep Myths: What Really Works?

Does age matter for biphasic sleep?

Age plays a role in how well biphasic sleep works.

Young children naturally sleep in multiple periods throughout the day. As they grow, they gradually consolidate sleep. Most children transition from two naps to one around 15 to 18 months, then stop napping between ages 3 and 5.

This happens at different times for different children. Research found that habitual nappers showed significant memory problems when prevented from napping, while children who had already transitioned maintained normal function [9]. The key for parents is watching individual children rather than following rigid timelines.

Teenagers need 8 to 10 hours of sleep, but often fall short. Their circadian rhythms shift later during adolescence, creating preferences for staying up late and sleeping in. A strategic afternoon nap after school could help catch up on lost sleep, though timing needs care to avoid interfering with nighttime sleep.

Adults do well with either monophasic or biphasic sleep, depending on circumstances. Work schedules typically matter more than age. Someone with a flexible remote job might thrive on a siesta schedule, while someone with a traditional office job may find it impossible.

Older adults experience sleep changes with age. They tend to sleep more lightly, wake up more frequently, and need slightly less total sleep (though still 7-8 hours). Many older adults who wake around 2 or 3 AM worry that something is wrong. Understanding that some nighttime waking is normal and that humans historically slept in two phases can reduce this anxiety.

How to try biphasic sleep

If you want to experiment with biphasic sleep, take a gradual approach.

Figure out your sleep needs first

Most adults require 7 to 9 hours. Track your current sleep and how you feel. Are you tired during the day? Do you need caffeine to function? Do you sleep much longer on weekends?

Your two sleep periods need to add up to your total requirement. If you need 8 hours, you might do 6 hours at night plus a 90-minute nap (7.5 hours total) or 7 hours at night plus a 30-minute nap (7.5 hours total).

Pick a pattern that fits your life

Time your nap right

Best time - Early afternoon between noon and 2 PM. This aligns with your body's natural dip in alertness.

Avoid - Late afternoon or evening (after 4 PM). These can interfere with nighttime sleep.

Start small

Don't immediately cut your nighttime sleep. Start by adding a 20 to 30-minute nap to your current schedule. Maintain this for a week or two. Once you're napping consistently, you can slowly adjust nighttime sleep if needed.

Keep it consistent

Pick specific times for both sleep periods and maintain them, including weekends. If you nap at 2 PM on weekdays but skip it on weekends, your body will struggle.

Set up your nap space

Your daytime sleep area should be:

• Dark (use curtains or an eye mask)

• Quiet (earplugs or white noise help)

• Cool (around 65-68°F)

• Comfortable

If napping at work, find a quiet spot. Some offices have wellness rooms or unused conference rooms.

Use an alarm

Set your alarm for your target nap duration. To avoid grogginess, either keep naps under 30 minutes or extend them to 90 minutes for a full cycle. Avoid the 30-60 minute range.

For segmented sleep, keep the middle quiet

If you're trying segmented sleep with a wakeful period between two nighttime sessions, keep activities calm. Read a physical book, do gentle stretches, meditate, or write in a journal. Avoid screens—blue light signals your brain that morning has arrived.

Track how you feel

Pay attention for at least 2 to 3 weeks. Your body needs time to adjust.

Monitor:

• Energy levels during the day

• Ability to concentrate

• Mood and emotional stability

• How easily you fall asleep at night

• Physical health changes

If you feel more tired, have trouble focusing, or find the biphasic sleep disrupts your life more than it helps, it may not be right for you.

Be willing to go back

Different patterns work for different people. If biphasic sleep doesn't improve your rest after a fair trial, returning to one sleep period is perfectly reasonable.

Is biphasic sleep safe?

Biphasic sleep is considered safe for people who can adapt without negative effects. However, it's not universally healthy and can be risky for others.

While historically common, the current and well-supported recommendation is getting at least 7 to 9 hours of sleep each night for optimal health. If you're considering trying biphasic sleep, consult your doctor to determine if it's appropriate for you.

For those struggling with sleep at night, experiencing fragmented sleep, or simply wanting more restful sleep, Sip2Sleep® can help. Just 1 to 3 full droppers before bed can support the peaceful sleep you need.

References:

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