March 8, 2023
With busy schedules that often keep us going non-stop throughout the day, many of us feel a lot of pressure to get as much sleep as we can to avoid exhaustion and performance dips. What if we told you it was natural to wake up an hour or two after you first fall asleep? What if we told you that before the late 1700s, many cultures around the world slept in two distinct phases of sleep: first and second sleep. The truth is that monophasic sleep (sleeping in one block of time per 24-hour period) is a relatively new human habit, reaching back only about 250 years. Prior to that, documentation collected by historians, notably by Roger Ekirch, PhD, suggests that most people regularly rested in two distinct segmented sleep patterns (biphasic sleep). Even today some cultures base their days around regularly scheduled breaks for naps!
What are Biphasic Sleep Patterns?
Biphasic sleep refers to sleep that’s divided into two sleep periods throughout the day. Rather than getting the recommended 7-9 hours of sleep all in one period, biphasic sleep breaks this into two segments.
This could look like a 1-3 hour “first sleep” beginning around 9 pm, followed by a period of wakefulness, before sleeping for another 5-8 hours. Or it might include a midday nap of 1-2 hours, with the final 6-8 hours of sleep collected in the evening.
Biphasic sleep is also called segmented, divided, and bimodal sleep.
Biphasic vs. Monophasic Sleep
Monophasic sleep refers to the way most of us in Western societies are used to organizing our sleep schedules, in a single period of 7-9 hours of nighttime sleep. While this may be the pattern our schedules demand, it may not be the most natural or beneficial to us.
Biphasic vs. Polyphasic Sleep
Polyphasic sleep refers to individuals who sleep in three or more periods. This could mean taking a 20-minute nap every four hours (Uberman Schedule) or taking three 20-minute naps during the day followed by three hours of sleep at night (Everyman Schedule).
While advocates of polyphasic sleep suggest it leads to improved cognitive performance and makes them feel more alert and productive, the research has not borne this out.
Studies on polyphasic sleep suggest that it often leads to sleep deprivation, as many of the schedules don’t achieve the 7-9 hours of sleep that are essential for most people.1
Beyond not getting enough sleep time, one study found that polyphasic sleep may have its own negative effects. The study found that even when participants got 7-9 hours of sleep with a polyphasic schedule, they experienced poorer academic performance. Additionally, participants also experienced interruptions in their circadian rhythm equal to traveling 2-3 time zones to the west.2
The Forgotten History of Biphasic Sleep
Unless you live in countries like Spain or Greece that still regularly hold space for mid-day naps, for many the idea of sleeping in anything other than one 7-9 hour block is mind-boggling.
But through the rigorous work of historians like Roger Ekirch, PhD, we now know that monophasic sleep patterns only became the norm starting with the industrial revolution (1760-1840).3
Prior to 1760, sleeping in two segments was actually far more common!
In his research, Ekirch found that many cultures regularly referenced a “first sleep” and a “second sleep.”
“First sleep” would typically take place roughly between 9 pm and 11 pm, at which point people would naturally wake up. For the next hour or two, they’d do any number of activities, from attending to household chores to taking care of livestock. Then at around 1 am, they’d head back to sleep to wake up with the rising of the sun.3
So what changed? With the invention and spread of electricity, people were no longer constricted to working in tandem with the sun. People began working longer hours, which meant that sleep schedules had to be condensed.
In other words, the way we sleep today can be considered an adaptation to the invention of electricity, and its impacts on how our societies function!
Biphasic Sleep Today
As we mentioned earlier, most cultures today practice monophasic sleep. Most…
David Samson, Researcher and Director of the Sleep and Human Evolution Laboratory at the University of Toronto, conducted an interesting study in 2015. Alongside others, Samson recruited a number of volunteers in northeastern Madagascar in the remote community of Manadena.3
What’s unique about Manadena is that it’s located right at the edge of a national park and has no electricity. This means that the people of Manadena experience nights as dark as they have been for most of human history.
The researchers then used “actimeters” to record the sleep cycles of the participants. At the end of one week, they found that most would wake for a period of activity between 12-1/1:30 am, before heading back to sleep and waking up with the rising of the sun.3
This suggests that electricity may truly have been the igniting spark that led to the sleeping schedules we have today.
That being said, there are many cultures today where daily life is scheduled around afternoon naps, including in Spain, Greece, Italy, and more.
Should You Try a Biphasic Sleep Schedule?
The research on biphasic sleep schedules comes in a few different forms.
Numerous studies have linked short naps of 20-30 minutes with benefits for alertness, performance, increased stress resilience, and even drops in inflammatory activity.4, 5, 6
Longer naps of 60-90 minutes allow you to go through a full sleep cycle, which can give you the added benefits that come with deep sleep. Research has found that 60-90 minute naps have led to improved learning, short-term memory, attention, tolerance for stress, and more.7, 8
The only catch with longer naps — you might have to go through sleep inertia or that initial state of grogginess that you usually experience when you first wake up. But if you’ve got some extra time to wake up after your nap, the added benefits could be worth it.
When it comes to the biphasic sleep schedules of our ancestors and the concept of “first sleep” and “second sleep,” research suggests this may be our normal evolutionary programing.
For instance, one small study in 1992 took 15 men and limited their access to light to just 10 hours a day, replicating light patterns from before the industrial revolution. After 4 weeks, all the participants had naturally shifted to biphasic sleep patterns.9
Ultimately, whether or not you should adopt a biphasic sleep schedule depends on your needs. If it helps you get more sleep, then biphasic schedules could benefit you!
Common Biphasic Sleep Schedules to Try Out
The most important thing is that- no matter the schedule, you still want to get 7-9 hours of sleep every 24-hour period!
The Mid-Day Catnap — Sleep for 6-7 hours at night plus a 20 or 30 minute power nap during the day.
Siesta Sleep Schedule — 5-6 hours of sleep at night and a 1-2 hour long nap in the afternoon.
Traditional “First” and “Second” Sleep — This pattern will likely mean you have to go to sleep earlier than usual. Sleep for 1-3 hours, wake up for 1-2 hours, then head back to sleep for another 6-8 hours.
If you’re struggling with getting a good night’s sleep, know that you’re not alone, and there are options.
Learn more about how Muse’s Digital Sleeping Pill could help you fall asleep more easily and sleep soundly through the night.
