What is Segmented Sleep? The Difference between Biphasic, Polyphasic & Monophasic Sleep

Dr. Colleen Ehrnstrom's profile picture
Dr. Colleen Ehrnstrom, PhD
Jun 1, 20225 min read
Owl sitting on a branch at night

Are you mono, bi, or poly? No, we’re not talking about your love life. We’re talking about your sleep patterns — how often you wake at night and nap during the day, and whether you are a monophasic, biphasic or a polyphasic sleeper. And, even more importantly, how do you perceive your sleep patterns? Are you a merry midnight waker, or do bouts of sleeplessness in the early morning make you feel anxious and tense?

Monophasic Sleep

If you are the type of person who puts down your head at ten and wakes up at six with no recollection of waking up in-between, you’re definitely a monophasic sleeper — the scientific term for people who get eight hours of solid shut-eye every night without major awakenings.

Biphasic Sleep

However, if you are someone who gets up in the middle of the night for a midnight snack, a cup of tea, or even a quiet (or not-so-quiet) early-hours chat with your roommates before settling in for the second stretch, you’re a biphasic sleeper. You probably sleep in two long stretches, broken by a period of wakefulness every night. You’re also biphasic if you like taking an afternoon nap or siesta and spend shorter intervals in your bed at night. In countries like Spain, for example, it is tradition to siesta for one to one and a half hours and then sleep again for five to six hours at night.

Polyphasic Sleep

Polyphasic sleepers, on the other hand, take segmentation to the next level. They sleep more than twice a day. They may put in a pre-midnight snooze, walk around the house between twelve and two, settle in for another stretch and take short siestas to rest their brains and bodies during the day. Interestingly, we all start out as polyphasic sleepers when we’re born.1

Segmented sleep

Both biphasic and polyphasic sleep are what experts called segmented sleep. Segmented sleep is any type of sleep pattern that involves sleeping in chunks or segments.

Segmented sleep is not necessarily a problem but it becomes one if you believe it to be so. The mantra that a solid, unbroken, eight-hour stretch of sleep is the gold standard is one of the most common and erroneous sleep perceptions that troubles people who experience sleep problems.Thousands of people who wake up in the middle of the night experience great anxiety because they believe their wakefulness is unnatural and unhealthy. This anxiety, more than the awakening itself, can interfere with healthy sleep patterns;worrying puts your brain in a state of hyperarousal, which interferes with your natural sleep drive .

The History of Segmented Sleep

However, research indicates that waking up during the night is often perfectly normal – a throwback to our pre-industrial past. Sleep researcher Roger Ehkirch points out that people in the pre-industrial era habitually slept in segments.2 His research, based on diaries, documents, books and medical literature, deduces that biphasic sleep occurred across the globe in Europe, North America, the Middle East, Africa, South Asia, Southeast Asia, Australia, and Latin America.

In other words, in the pre-industrialized world our ancestors slept in shifts and thought nothing of it. Biphasic sleep – historically dubbed the “first” and the “second” sleep – were perfectly normal. It is likely that artificial illumination, along with work and school schedules, started extending active hours and shifting when, and how, sleep cycles occurred.

Ehkirch says the consolidated sleep to which the industrialized world aspires is for Western societies “a remarkably youthful form of sleep, a product not of the primeval past but of forces grounded in technology (artificial illumination) and shifting cultural attitudes toward sleep over the course of the Industrial Revolution.”3

Is Segmented Sleep Good or Bad For Me?

Sleep patterns are not a one-size-fits all affair. Sleep is not a passive state. You sleep in stages , which range from very light sleep to deep sleep. And different people have different sleep cycles, depending on factors such as their circadian rhythm .

Segmented sleep can be unhealthy if all your sleep segments in a 24-hour period do not add up to the total number of hours of sleep you need to function properly. But for different people this figure is different. There is no hard-and fast rule. Some people are genetically inclined to need less sleep.4

A 2021 survey done in India even found that medical students performed better academically if they slept segmentally rather than monophasically and that segmental sleepers did not suffer from daytime sleepiness as much as monophasic sleepers did.5

When Is Polyphasic Sleep Unhealthy for Me?

Polyphasic sleep is sometimes associated with neurodegenerative illnesses like Alzheimer’s and dementia. And it can become a problem if you’re sleeping polyphasically because you’re stressed or depressed. Or if your job causes multiple interruptions of your natural circadian rhythms over a 24-hour period. Doctors, nurses and night-shift workers, for example, may experience fatigue as a result of such forced polyphasic sleeping patterns.

The Journal Sleep Health warns that polyphasic sleep schedules, and the sleep deficiency inherent in those schedules, are associated with a variety of adverse physical health, mental health, and performance outcomes.6 However, if a polyphasic rhythm works for you and allows you to function optimally, there is no reason why you shouldn’t follow this rhythm.

If you are worried about waking up at night, fill in our questionnaire and talk to our experts to discover if your biphasic or polyphasic sleep patterns are optimal for you.


  1. Sudhansu Chokroverty, Sudhansu. (1994). Sleep disorders in Sleep Disorders Medicine, 7-16. Butterworth-Heinemann. https://doi.org/10.1016/B978-0-7506-9002-7.50007-0.

  2. Ekirch A. R. (2016). Segmented Sleep in Preindustrial Societies. Sleep, 39(3), 715–716. https://doi.org/10.5665/sleep.5558

  3. Ekirch, A. (2015) The modernization of Western sleep: or, does insomnia have a history? Past & Present, 149–92.

  4. Hirano, A et al. (2018) DEC2 modulates orexin expression and regulates sleep. PNAS, 115 (13), 2434 – 3439. https://doi.org/10.1073/pnas.1801693115.

  5. Shalini S.P. et al. (2021) Effect of Segmented Sleeping on the Academic Performance of Medical Students. A Questionnaire Survey. Medico-legal Update, January-March 2021, Vol. 21, No. 1.

  6. Weaver, MD et al. (2021) Adverse impact of polyphasic sleep patterns in humans: Report of the National Sleep Foundation sleep timing and variability consensus panel. Sleep Health, 7 (3), 293-302. https://doi.org/10.1016/j.sleh.2021.02.009.

Dr. Colleen Ehrnstrom's profile picture
Dr. Colleen Ehrnstrom, PhD

Dr. Colleen Ehrnstrom is a licensed clinical psychologist with a specialty practice in Acceptance and Commitment Therapy (ACT). Areas of expertise include insomnia and other sleep disorders, anxiety, and depression.

Dr. Ehrnstrom is not a medical provider and is not providing any recommendations regarding medications. Rather, she is sharing and reviewing the research as it relates to education when learning how best to treat insomnia.

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