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Sleeping in two shifts - were our ancestors on to something?

We’re all too familiar with the notion that we’re not getting enough sleep. And we’re well aware that the sweet spot is 7-8 hours of decent sleep every night.  But, even if we were able to get to bed earlier, or sleep in that little bit later, would we be able to stay asleep for 8 hours straight? For many of us, being woken by the need to visit the bathroom, or a baby’s cry, or a dog barking is enough to have us tossing and turning for hours, unable to fall back into deep slumber.  Approximately one third of the population is affected by frequent sleep difficulties which include initiating and maintaining sleep, and experiencing inadequate sleep. This has led to us asking the question - is it natural to do one big block of sleep?

There’s a growing body of evidence from both science and history that shows that perhaps the 8 hour sleep (in one block) is a more recent trend and that it may not be the most natural way to sleep.  Could it be that a period of wakefulness during sleep should not be stressful, but rather, something that used to be the norm?

Learning from the past

There have been numerous historical accounts of segmented sleep, from medical texts, to court records, diaries and literature which reference a ‘first’ sleep and a ‘second’ sleep.  Anthropologists have found evidence that bi-modal sleeping was the norm during Pre-industrial Europe.  A first sleep would commence about two hours after dusk and would be followed by a waking period of 1-2 hours before a second sleep. During this wakeful period, people certainly weren’t tossing and turning in the contrary in fact.  They were often up and about, going to the toilet, smoking tobacco, even visiting their neighbours! Others stayed in bed, read, prayed or wrote and conversed (or otherwise) with their bed-partners. Doctors even recommended that the best time to conceive was after this first sleep, when the body was rested!

By the 1920s references to the first and second sleep disappeared and the idea seems to have slipped from our social consciousness.  Interestingly this coincides with the appearance of ‘sleep maintenance insomnia’ in literature.  Is it possible that waking up during the night, is historically a part of our normal physiology?

What the studies tell us

Adding further evidence to this idea was a sleep study by psychiatrist Thomas Wehr in 1990.  Wehr deprived participants of artificial light for 14 hours each day over a month. The subjects were able to sleep as much as they wanted during the experiment. As you might expect, at first they slept a lot - an average of 11 hours a night, making up for sleep deprivation they were experiencing in their day to day life.  But once they were well rested it was found that they slept for 8 hours a night, in two separate blocks. The first block of sleep was for an average of three to five hours. Then they would wake for one to two hours in a restful state before a second three to five hour period. It was suggested from this experiment, free from the constraints of modern life, that a biphasic pattern of sleep is our natural tendency

What to do with what we know?

For most of us, it’s difficult enough to find 8 consecutive hours in the day to sleep, let alone find an extra couple of hours to incorporate a ‘waking period’ into our sleep schedule.  But if we consider that a wakeful period during the night, could be part of our natural make up, then perhaps we can reduce the sleep anxiety that we experience in the middle of the night. The worry that we are doing something wrong, or that we’re not getting enough sleep, is often part of the insomniac’s problem.

An acceptance of the notion that consecutive sleep hours are not ‘the be all and end all’ could also lead to a greater tolerance in our society and work places to napping.  Napping (link to our nap article) has been proven to have important benefits for mood, memory and learning and increasing alertness.

No one denies that adequate sleep is essential, but let’s free ourselves from rigid ideas about what constitutes a good night’s sleep and maybe we can all immediately feel a little more relaxed!




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