What you need to know about biphasic and polyphasic sleep
Everybody is busy these days, looking to squeeze as much as they can out of every moment of the day, and night. Sure, you know you need roughly eight hours of sleep—but wouldn’t it be great if you could somehow get that ‘ideal eight’ in five hours? (Hint: it’s possible, but not too healthy.)
I have patients who are interested in bio-hacking their sleep, whether to maximize their time efficiency, or to boost performance, or both. This often leads to a discussion of biphasic and polyphasic sleep, and whether it’s a good idea to try.
Not familiar with polyphasic sleep? You’re in good company. As you’re about to learn, although these sleep patterns may have an ancient history, they’re kind of new all over again, as people look for ways to maximize the efficiency of their rest. It’s a good time to take closer look at these sleep patterns—what science tells us about their history, how people are using them today, and what risks are associated with them.
What are biphasic and polyphasic sleep?
These are patterns of sleep that involve sleep in segments, rather than in a single, uninterrupted block of time. Think about the sleep pattern most of us keep: a stretch of 7-8 hours a night asleep, followed by a long, usually unbroken stretch of wakefulness of about 16 hours, before dropping back into sleep. That sleep pattern, so common in the United States and much of the industrialized world, is known as “monophasic sleep.”
Biphasic and polyphasic sleep break up that single period of sleep into segments of rest that occur at different times throughout the day and night.
Biphasic sleep divides sleep into two parts. It may involve a long stretch of sleep overnight, with a much shorter block of sleep during the day. A 6-hour nightly sleep period might be paired with a 30-90 minute nap during the day.
Biphasic sleep is sometimes known as “siesta sleep,” a nod to some Western cultures, including Spain and Greece, that continue to incorporate the afternoon rest as part of their cultures and commonly-held sleep patterns.
Polyphasic sleep breaks up sleep into more than two episodes throughout the day and night. Polyphasic sleepers might sleep as many as six times a day, in some combination of 2-3 hour blocks of sleep and 30-90 minute naps, which over 24 hours are meant to add up to the equivalent of a full night of rest.
These may sound like new approaches to sleep—but there are scientists and historians who think that forms of polyphasic and biphasic sleep patterns have an ancient history, and were once the norm for human sleep. Research over the past couple of decades suggests that our ancestors, for most of human history, may have relied on biphasic sleep patterns. The shift to the 8-hour night of sleep may have been a relatively recent development, one that was spurred on by industrialization and widespread access to electricity and artificial light. Some scientific findings suggest that our ancestors sleep patterns may have included a stint of sleep lasting 3-5 hours, followed by a period of time awake, engaging in some light activity, followed by another stretch of 3-5 hours of sleep.
If you imagine the daily patterns of life in a pre-industrial, pre-electric age, this pattern makes some sense. Living closely in sync with natural daylight, the first phase of sleep would have likely come with the onset of darkness. That stretch of darkness, lasting 12 hours or more, would have been a long time to sleep without interruption. Waking partway through, to have something to eat, have sex, or engage is some other light activity, could likely have been common practice, before falling back to sleep before waking at dawn.
These segmented sleep patterns may indeed have a long history among humans—but does that mean they make sense for us today? Sleep is influenced by many factors, some biological, and others social. Switching to a segmented sleep routine is no simple matter—and for most people, it’s not practical or advisable.
Sleep rhythm and sleep drive
We don’t just decide to sleep and instantly make it happen. Sleep doesn’t operate on the flick of a switch. There are internal and external forces that influence when we’re more, or less, able and inclined to sleep. Two primary biological forces are sleep rhythm and sleep drive.
Sleep drive is the internal need for sleep, which gets stronger the longer you are awake. Sleep drive is at its lowest after you’ve awakened from a solid night of rest, and highest when you’ve been awake and active for many hours. Throughout the day, it gradually increases. A poor night of sleep will leave your sleep drive higher during the day—those are the days when you feel yourself wanting to nod off at 3 p.m.
If sleep drive were the only force at work, you can imagine how a polyphasic sleep pattern might be the norm. You’d sleep for a while, be awake and active for a period of time, and then sleep some more. Your sleep patterns might look something like a cat’s—a series of naps throughout the day and night.
But another powerful force influences our sleep: the sleep rhythm. Governed by the circadian clock, which in turn takes its cues primarily from light and darkness—the 24-hour sleep-wake rhythm works to promote alertness during the day, and sleep during the night, with peaks and dips throughout the 24-hour day. The sleep hormone melatonin is a key player in the body’s circadian sleep rhythm, rising at night to help initiate sleep, and falling during the day to allow for energy and alertness.
These two systems work simultaneously to regulate a 24-hour sleep wake cycle that largely consolidates sleep and wakefulness into relatively long stretches during the night and day.
Of course, society’s influence also plays a significant role in providing a framework for sleep—and encouraging a monophasic sleep routine. Work, school, family routines and social activities all largely conform to this schedule of consolidated sleep at night, and wakefulness during the day. One of the biggest challenges to adopting a biphasic or polyphasic sleep routine is the limitations it can place on social interaction.
Everyone’s circadian sleep rhythm and internal sleep drive function a little differently. Some people are naturally more inclined to sleep soundly for eight hours in a single stretch—while others may have some natural, biological inclination toward shorter periods of overnight sleep with some additional sleep during the day.
Before you consider adopting a biphasic or polyphasic sleep pattern, there are important factors to consider.
What science says about biphasic sleep
There hasn’t been an abundance of scientific attention given to rigorous study of these sleep patterns. Evidence suggests humans may have some biological inclinations toward segmented sleep routines. But there’s also evidence indicating that segmented sleep patterns may increase risks for insufficient sleep, health problems, and performance issues.
A study conducted in the early 1990s investigated biphasic sleep by re-creating the night-day conditions of pre-industrial life. Subjects spent four weeks in 10 hours of light and 14 hours of darkness, daily. Over that four-week period, their sleep naturally shifted into distinct segments of several hours apiece, with a period of wakefulness in between. Research also found corresponding changes to the timing of the release of the sleep hormone melatonin, suggesting a shift in circadian rhythms.
The most approachable version of a biphasic sleep schedule involves a longer period of nighttime sleep, combined with a daytime nap. Studies of naps show they can offer benefits to cognitive function, alertness, and performance—but scientists take care to point out that more research is needed to fully understand the impact, benefits, and possible downsides of regular napping. Naps also can be useful for certain segments of the population, including shift workers. Research shows that among shift workers, timed naps can decrease sleeplessness and improve performance.
I’m a proponent of napping—but it needs to be done right. When not managed correctly, naps can interfere with nighttime sleep. Scientific evidence indicates that long and frequent naps elevate risk of poor nighttime sleep and create more, not less, sleep deprivation. Excessive and poorly timed sleep during the day may undermine also undermine cognitive function, and mood. (I’ll talk more about napping in an upcoming article.)
Biphasic and polyphasic sleep: what you need to know
I can’t go so far as to recommend a biphasic or polyphasic sleep routine, generally or for any particular group of people. I’m just not convinced, at this point, that these alternate sleep routines can deliver the quantity and quality of sleep people need on a regular basis.
What is clear are some of the challenges associated with maintaining a segmented sleep schedule. In addition, there are people who definitely shouldn’t attempt to use these sleep routines.
Managing a biphasic or polyphasic sleep routine is NOT about napping here and there, when the mood strikes. These sleep patterns require a strict schedule, to ensure you’re getting sufficient sleep. No matter how much you’d like to, you can’t get eight hours of sleep in five hours. Consistency is crucial to healthy sleep, no matter what sleep schedule you follow.
Because of the strict schedule that’s necessary to get healthy sleep using biphasic or polyphasic sleep patterns, these routines can be socially limiting. Remember, switching to these sleep patterns means putting yourself squarely at odds with society at large. You’re likely to regularly face difficult choices between participation in social and professional activities, and getting the sleep you need at its appointed time.
Anyone with a proclivity for depression or other mental health disorders should not adopt these sleep patterns. I’ve seen people who are predisposed to depression use biphasic sleep and go on to develop major depressive disorder, or MDD. Depression and other mood disorders are associated with disruptions to circadian rhythms, as well as with disrupted sleep patterns and poor-quality sleep. Attempting to use a segmented sleep schedule could destabilize sleep patterns and circadian rhythm, worsening sleep and exacerbating mood disorders.
I understand the interest in these sleep routines, and in trying to make the most of every hour in the day. I’ll continue to watch with interest as these sleep patterns are subjected to more scientific study. Ultimately, there are no real short-cuts to healthy sleep. The smartest time management strategy is to focus on getting the high-quality sleep you need at night, and taking full advantage of all the physical, emotional, and cognitive power that your night sleep gives you during your waking day.
Michael J. Breus, PhD, DABSM
The Sleep Doctor™