There is every reason to believe that segmented sleep … had long been the natural pattern of our slumber before the modern age, with a provenance as old as mankind.A. Roger Ekirch
The common advice to get eight hours of sleep at night may not be a natural way of sleeping. Some historians and scientists believe that it is only in the modern day that people began sleeping this way.
In 2014 Valerie Robin, a student in Atlanta, embarked on an experiment. She went to bed when it got dark and woke up with the morning light. This might not seem particularly unusual, except that Valerie went to bed early so that she could wake up in the middle of the night to read, write in her journal and talk on the phone with friends in other time zones.
Far from being sleep-deprived by this unusual life-style choice, she reported feeling calm, rested and energised. She concluded that this was a healthier way of sleeping than the recommended eight-hour sleep. [You can read about Valerie’s experiment here]
Valerie began her experiment after reading about a way of sleeping that historians and sleep scientists call biphasic sleep. Instead of sleeping for one eight-hour stretch through the night, a person sleeps for a shorter period (called ‘first sleep’), wakes up in the middle of the night to quiet contemplation or to get on with some task, and then falls asleep again until morning (the ‘second sleep’).
Sleep experts now believe that this is an entirely natural sleep pattern. It was how our ancestors slept before the Industrial Revolution.
Segmented sleep is a pattern of sleep that is broken up into sections throughout the day or night.
We have all experienced segmented sleep at some point in our lives. Babies sleep in short phases throughout the day and night. As we age, we return to something like this broken up form of sleep.
A newborn baby sleeps in four-hour cycles throughout the day and night. On average she is awake for two hours, sleeps for two hours, and then wakes again wanting to feed. This is known as polyphasic sleep.
A four-year-old will sleep through the night, but will want to nap in the afternoon – biphasic sleep.
This kind of two-phase sleep (night-time sleep with the addition of a nap) is also traditional in countries where people take a nap in the early afternoon called a siesta. The siesta was popular in countries where it is very hot in the middle of the day, although the practice is becoming less common with globalisation.
For most of our later childhood and adult life we sleep during the night for around six to ten hours and are awake during the day. Unless we have to work a night shift or suffer from a sleep disorder, we expect to sleep through the night and wake up when the alarm goes off in the morning.
This is called monophasic sleep.
Sleep We Have Lost
What if broken sleep is normal? Today segmented sleep is viewed as unhealthy, except in young children and the elderly. However, the historian A. Roger Ekirch has uncovered evidence that our ancestors expected to wake in the night.
They experienced a form of biphasic sleep in which they slept for a few hour and then woke up for an hour or more in the middle of the night before going back to sleep again until morning. The first period of sleep was called ‘first sleep’ and the period of sleep in the morning was called ‘second sleep’.
This period of quiet wakefulness was not seen as abnormal of unhealthy. In fact, it could be quite productive. People used this time for quiet contemplation, spiritual devotion, to respond to a call of nature, smoke a pipe or even get on with chores.
Leonardo da Vinci believed that the the darkness of the night was a good time to turn over original ideas in the mind. More mundanely, a servant called Jane Addison got up in the middle of the night to brew ale.
The Wehr Experiment
Every time we turn on a light we are inadvertently taking a drug that affects how we will sleep.Charles A. Czeisler, chronobiologist
Why did our sleeping patterns change? An experiment by the psychiatrist Thomas Wehr may provide a clue.
In the 1990s a group of volunteers spent some weeks in an environment that recreated the long winter day before modern electric light. For ten hours each day the volunteers were exposed to both artificial light and daylight, but for fourteen hours during the night they were submerged in darkness.
Wehr’s findings on observing the sleeping patterns of his volunteers are striking. They each slept for a period of three to four hours before waking in the night to spend some time in quiet wakefulness. They then fell asleep again for a ‘second sleep’ towards the morning.
As Valerie found during her experiment, the volunteers described this period of wakefulness as like a kind of meditation, free from the stress normally associated with insomnia.
Sleep experts have concluded from Wehr’s experiment that exposure to powerful modern lighting, which turns night into day, has altered the way in which we sleep.
My thanks to Richard Horner for kindly providing the diagram on sleep patterns across the lifespan.
Richard Horner, The Universal Pastime: Sleep and Rest Explained (2014)
A view of sleep from a neurobiologist. You can read more about segmented sleep in chapter seven.
A. Roger Ekirch, At Day’s Close: A History of Nighttime (2005)
A history of night-time activity in Europe before the Industrial Revolution. Ekirch explains his theory of ‘first’ and ‘second’ sleep in chapter twelve (Sleep We Have Lost: Rhythms and Revelations).