The term biphasic sleep simply refers to the idea of breaking the sleep period up into 2 distinct and separate time periods.
Almost all of us do all of our sleeping during one period of time each day. But is that really the best way? Some studies suggest that humans will naturally adopt this biphasic style of sleeping when they’re deprived of clocks and external time cues like the sun.
But is biphasic sleep a viable alternative for you? Let’s take a look.
Biphasic Sleep In History
Historian A. Roger Ekirch has argued that before the Industrial Revolution, interrupted sleep was dominant in Western civilization. He draws evidence from documents from the ancient, medieval, and modern world. Other historians, such as Craig Koslofsky, have endorsed Ekirch’s analysis.
According to Ekirch’s argument, adults typically slept in two distinct phases, bridged by an intervening period of wakefulness of approximately one hour. This time was used to pray and reflect, and to interpret dreams, which were more vivid at that hour than upon waking in the morning. This was also a favorite time for scholars and poets to write uninterrupted, whereas still others visited neighbors, engaged in sexual activity, or committed petty crime.
The human circadian rhythm regulates the human sleep-wake cycle of wakefulness during the day and sleep at night. Ekirch suggests that it is due to the modern use of electric lighting that most modern humans do not practice interrupted sleep, which is a concern for some writers. Superimposed on this basic rhythm is a secondary one of light sleep in the early afternoon.
The modern assumption that consolidated sleep with no awakenings is the normal and correct way for human adults to sleep, may lead people to consult their doctors fearing they have maintenance insomnia or other sleep disorders. If Ekirch’s hypothesis is correct, their concerns might best be addressed by reassurance that their sleep conforms to historically natural sleep patterns.
Ekirch has found that the two periods of night sleep were called “first sleep” (occasionally “dead sleep”) and “second sleep” (or “morning sleep”) in medieval England. He found that first and second sleep were also the terms in the Romance languages, as well as in the language of the Tiv of Nigeria.
In French, the common term was premier sommeil or premier somme; in Italian, primo sonno; in Latin, primo somno or concubia nocte. He found no common word in English for the period of wakefulness between, apart from paraphrases such as first waking or when one wakes from his first sleep and the generic watch in its old meaning of being awake. In old French an equivalent generic term is dorveille, a portmanteau of the French words dormir (to sleep) and veiller (to be awake).
Because members of modern industrialised societies, with later evening hours facilitated by electric lighting, mostly do not practice interrupted sleep, Ekirch suggests that they may have misinterpreted and mistranslated references to it in literature. Common modern interpretations of the term first sleep are “beauty sleep” and “early slumber”. A reference to first sleep in the Odyssey was translated as “first sleep” in the seventeenth century, but, if Ekirch’s hypothesis is correct, was universally mistranslated in the twentieth.
In his 1992 study “In short photoperiods, human sleep is biphasic”, Thomas Wehr had eight healthy men confined to a room for fourteen hours of darkness daily for a month.
At first the participants slept for about eleven hours, presumably making up for their sleep debt. After this the subjects began to sleep much as people in pre-industrial times had. They would sleep for about four hours, wake up for two to three hours, then go back to bed for another four hours. They also took about two hours to fall asleep.
Biphasic sleep typically involves:
A core sleep period of 3 – 4.5 hours
A secondary sleep period of 90 minutes. Many people affectionately refer to this period of sleep as a “nap.” The 90-minute time frame is important because most people have a sleep cycle of 90 minutes. A quick catnap is not the same thing.
One example of a biphasic sleep pattern is the practice of siesta, which is a nap taken in the early afternoon, often after the midday meal. Such a period of sleep is a common tradition in some countries, particularly those where the weather is warm.
The siesta is historically common throughout the Mediterranean and Southern Europe. It is the traditional daytime sleep of India, Spain, through Spanish influence, China, the Philippines, and many Hispanic American countries.
Your greatest challenge, especially if you are not in one of those countries, is likely to be fitting the nap into your schedule. Ideally, you could nap when you’re most tired. This seems to be in the afternoon for many of us.
Think about how tired you feel at around 3:00 every afternoon at work. Unfortunately, having a nap then won’t work if you’re at your job.
Instead, either just before or after dinner is the most common time for working people to schedule their biphasic nap.
According to it’s proponents, benefits of biphasic sleep include the following:
Reduced total time spent sleeping. Biphasic sleepers can commonly get down to 4.5 total hours of sleep without being tired. A couple extra hours of free time could be put to good use
Improved quality of sleep. Biphasic sleepers report that their sleep quality is deeper and better
More dream recall. For those who like to analyze their dreams, these decreased periods of sleep appear to improve recall of dreams.
One known disadvantage is interacting with non-biphasic sleepers. Your significant other, your children, or your boss may not appreciate you disappearing to take a 90-minute nap.
And the biologist and researcher Piotr A. Woźniak considers the theory behind severe reduction of total sleep time by way of short naps unsound, arguing that there is no brain control mechanism that would make it possible to adapt to the “multiple naps” system.
Woźniak argues that the body will always tend to consolidate sleep into at least one solid block, and he expresses concern that the ways in which the polyphasic sleepers' attempt to limit total sleep time, restrict time spent in the various stages of the sleep cycle, and disrupt their circadian rhythms, will eventually cause them to suffer the same negative effects as those with other forms of sleep deprivation and circadian rhythm sleep disorder.
Starting a biphasic sleep program is easy. Simply take a nap for 90 minutes in the early evening and then go to bed three to four hours later than normal.
You can expect to be tired for the first week. Commonly, 21-28 days are required to really evaluate if biphasic sleep is for you.
Some questions to ask yourself after the trial period:
“How do I feel?” Are you tired all the time or do you feel refreshed?
“How is my productivity?” Are you holding your own at work? How’s your performance relative to before the experiment? How’s your activity level around the house?
“How is this change affecting my life?” Does biphasic sleep fit well with your lifestyle or is it causing challenges?
If you’re using the extra time to your advantage and there haven’t been any negative consequences, then congratulations. Many people, however, find that biphasic sleep creates challenges with family life. If that’s the case, you’ll need to determine how severe the issues are and how important biphasic sleep is to you.
Biphasic sleep can reduce the time you spend sleeping and also improve the quality of your sleep. While this lifestyle isn’t convenient for everyone’s schedule, it may be worth a trial run for three to four weeks.
You’ll know whether or not it’s working for you.
Mark Ehrman, Sara Mednick Take a Nap! Change Your Life. Workman Publishing Company; (2006) ISBN-13: 978-0761142904