I’ve been a lifelong insomniac from birth, so the brief module on the psychology of sleep that I covered in my first degree was of great interest to me. But what I didn’t realise until much later was that if we add some information from history of human sleeping patterns to what we know about the psychobiology of sleep, we can suggest many useful tips to people who report suffering from insomnia.
The basic biology of sleep
To start from basic biology, our ‘circadian rhythms’ – natural internal rhythms in hormonal and neurological balances that happen over the course of a day – are the basis of what is known as ‘arousal.’ This daily pattern of fluctuations in our internal biology make us feel sleepy at some times of the day and wide awake at others.
A normal circadian rhythm involves a low arousal state during the dark hours, and although we move through patterns of deeper and lighter sleep, A ‘normal’ pattern of sleep is nowadays typically reported to be 6–8 hours overnight.
Sleep patterns tend to degrade over the lifetime (older adults not only have more interrupted sleep, REM – or dreaming – sleep also reduces). And while it’s not unusual for anyone to wake briefly during the night, it is more likely to happen to older people.
Stress can also intrude by interfering with our ability to sleep both when we first go to bed, and by preventing us from getting back to sleep when we wake in the middle of the night. These are the two most common forms of reported insomnia. Being unable to get back to sleep once we’ve ‘topped up’ with two or three hours is generally experienced as more problematic, because it’s indicative of deep unresolved stress. It indicates that the body is only taking the minimum amount of sleep required and then waking the person to continue a vigilance against threat.
In hunter-gatherer societies, this syndrome, if short-lived, would have of course been adaptive – you would be far more likely to survive if you only took the minimum amount of sleep whilst being stalked by enemies or wild animals. But as an ongoing condition, not only do continually short hours of sleep interfere with getting sufficient rest in general, there is also a heavy impact upon REM or ‘Rapid Eye Movement’ sleep – which is crucial for psychological health.
The importance of dreaming
We knew very little about the importance of REM sleep until approximately seventy years ago, when physiologists Nathaniel Kleitman and Eugene Aserinsky found that, in human infants, periods of ‘active’ sleep were marked by rapid eye movements, and that these active sleep periods were on a regular cycle, alternating with quiet sleep periods.
Like many good scientific discoveries, this one was largely accidental. Aserinsky, the junior partner in the study, had hooked his eight-year-old son up to a brain wave machine, and left the child watching a display for a short time, while he looked at some papers. When he went back to the machine, it was recording brainwaves that suggested the child was still awake. But in fact, he had fallen asleep.
Several years later Kleitman and Dement showed that these rapid eye movements in human adults were correlated with specific brainwave patterns and that REM signalled the phase of sleep in which dreaming occurred.
As Aserinsky had discovered, REM sleep is marked by a waking-like EEG pattern, so it is sometimes referred to as ‘active sleep’ or, when the repression of movement by the brain during REM is also taken into account ‘paradoxical sleep’.
We now know that all land mammals and birds have periods of REM sleep, but that this differs between species; for example horses and giraffes have much less than cats and ferrets. A common finding between mammal species is that babies spend most of their sleep in REM (denoting rapid brain development) and this gradually decreases as they grow older, in humans plateauing in middle age.
A human adult typically has 90 minutes in REM in a 7–8-hour sleep period, and each REM episode is typically 10 minutes in length.
Later research indicated that REM sleep appears to facilitate learning and memory consolidation by selectively eliminating and maintaining new synapses – the physical structures we build in the brain when making new memories.
Recent research points to that poor or ‘restless’ REM sleep may impact upon people’s ability to overcome emotional distress, raising their risk for chronic depression or anxiety; that lack of or poor-quality REM sleep impacts on our ability to regulate our emotions. Feeling cranky when we’ve slept badly is, of course, something we can all relate to.
An important lesson from history
So, are people who frequently experience interrupted sleep heading for poor health? If they are sleeping very little, possibly so. But if the problem is interrupted sleep where the duration adds up to six hours or more a day, possibly not.
Surprisingly, the evidence for this comes from history, rather than psychology.
In the early 1990s, historian Roger Ekirch was researching a history of night-time. He was worried about his sleep chapter – he thought he might not find anything particularly interesting.
But as he researched 17th Century court records he found reference to a term he had never heard before: first sleep. Historians often research court records because they find many references to daily life in the specific period that shed light on mundane daily practices that died out many years ago. And this was an intriguing one.
Ekirch used ‘first sleep’ as a search term. He found this, and later, ‘second sleep’, turned up many historical records in letters, diaries, medical textbooks, newspapers and plays, and even the writings of Geoffrey Chaucer. First sleep was also recorded in French historical records as ‘premier somme’ in Italian records as ‘primo sonno’ and in many other languages across the world. Even the Romans had referred to it.
What Ekirch had found was that prior to the industrial revolution and street lighting, the typical way for human beings to sleep was in two phases, which he eventually called ‘biphasic sleep’. Biphasic sleep typically started with a short ‘first sleep’ from approximately 9pm to 11pm and a longer ‘second sleep’ from approximately 1am until dawn. Ordinary people in these times had little concept of telling the time by a clock; the sun was their guide.
The period between 11pm and 1pm was commonly known as ‘the watch’. People commonly chatted, cuddled (a lot of communal sleeping in those days – Samuel Pepys is quite informative on that point in his diary), checked on animals, set beer to brew and bread to rise, and of course in a more religious world, for some this was a time for prayer.
Flexible biphasic sleep
When Ekirch published his research, psychologists and sociologists were intrigued. They found that people deprived of light for 14 hours a day naturally fell into a biphasic sleeping pattern with a 1–3-hour break between the two sleep periods, and that their internal circadian rhythms altered to match. Sociologists later found that people in current day remote areas with no artificial lighting typically engage in biphasic sleeping.
It has also been speculated that the variation in circadian rhythms between individuals that is commonly labelled as ‘night owls’ and ‘morning larks’ is rooted in evolution; if members of a tribe are on slightly different biphasic sleeping schedules this would make it less likely that everyone would be asleep at the same time. This may even have been the basis for the traditional term for the waking period in biphasic sleeping: ‘the watch’.
Historian Sasha Handley found that, in by the mid-18th century, a set of diverse records begin to appear in UK archives that complain of increased after-dark socialisation, facilitated by oil lamps and street lighting, impacting upon sleep patterns. Older people began to complain that the ‘rest and silence that used to begin at 8pm and end at 6am’ was no longer observed. In 1754 an elderly lady complained in a letter that her first sleep was “being constantly broken by street noise”.
Useful lessons from biphasic ancestors
So, if you commonly wake up in the early hours of the morning and lay wide awake, running problems through your mind, wondering how and when you will be able to get back to sleep, perhaps the best response is to do something until you feel sleepy again, in the way of our bi-phasic ancestors.
However, our ‘disturbance’ problems go well beyond those of our ancestors, just beginning to cope with the differences that artificial light had begun to make to their daily round. The type of ‘something’ people living modern networked lives are tempted to do, such as clear a few emails, or complete urgent work that is hanging over from the previous day is highly likely to heighten stress and therefore hamper a smooth return to sleep.
If, however, we take some tips from our biphasic ancestors, and do something that doesn’t involve bright light, or engaging with the world wide web, we may experience fewer problems. History indicates that there is nothing wrong or harmful about biphasic sleeping. The best way to develop healthy biphasic rhythms is to avoid bright light and stress-provoking activities during the ‘watch’ (or wakeful period) in order to facilitate a smooth pathway back into sleep, and those all-important dreams.