2012-02-23 07:12:57
By Stephanie Hegarty BBC World Service
We often worry about lying awake in the middle of the night - but it could be
good for you. A growing body of evidence from both science and history suggests
that the eight-hour sleep may be unnatural.
In the early 1990s, psychiatrist Thomas Wehr conducted an experiment in which a
group of people were plunged into darkness for 14 hours every day for a month.
It took some time for their sleep to regulate but by the fourth week the
subjects had settled into a very distinct sleeping pattern. They slept first
for four hours, then woke for one or two hours before falling into a second
four-hour sleep.
Though sleep scientists were impressed by the study, among the general public
the idea that we must sleep for eight consecutive hours persists.
In 2001, historian Roger Ekirch of Virginia Tech published a seminal paper,
drawn from 16 years of research, revealing a wealth of historical evidence that
humans used to sleep in two distinct chunks.
His book At Day's Close: Night in Times Past, published four years later,
unearths more than 500 references to a segmented sleeping pattern - in diaries,
court records, medical books and literature, from Homer's Odyssey to an
anthropological account of modern tribes in Nigeria.
A woman tending to her husband in the middle of the night by Jan Saenredam,
1595 Roger Ekirch says this 1595 engraving by Jan Saenredam is evidence of
activity at night
Much like the experience of Wehr's subjects, these references describe a first
sleep which began about two hours after dusk, followed by waking period of one
or two hours and then a second sleep.
"It's not just the number of references - it is the way they refer to it, as if
it was common knowledge," Ekirch says.
During this waking period people were quite active. They often got up, went to
the toilet or smoked tobacco and some even visited neighbours. Most people
stayed in bed, read, wrote and often prayed. Countless prayer manuals from the
late 15th Century offered special prayers for the hours in between sleeps.
And these hours weren't entirely solitary - people often chatted to bed-fellows
or had sex.
A doctor's manual from 16th Century France even advised couples that the best
time to conceive was not at the end of a long day's labour but "after the first
sleep", when "they have more enjoyment" and "do it better".
Ekirch found that references to the first and second sleep started to disappear
during the late 17th Century. This started among the urban upper classes in
northern Europe and over the course of the next 200 years filtered down to the
rest of Western society.
By the 1920s the idea of a first and second sleep had receded entirely from our
social consciousness.
Continue reading the main story
When segmented sleep was the norm
"He knew this, even in the horror with which he started from his first sleep,
and threw up the window to dispel it by the presence of some object, beyond the
room, which had not been, as it were, the witness of his dream." Charles
Dickens, Barnaby Rudge (1840)
"Don Quixote followed nature, and being satisfied with his first sleep, did not
solicit more. As for Sancho, he never wanted a second, for the first lasted him
from night to morning." Miguel Cervantes, Don Quixote (1615)
"And at the wakening of your first sleepe You shall have a hott drinke made,
And at the wakening of your next sleepe Your sorrowes will have a slake." Early
English ballad, Old Robin of Portingale
The Tiv tribe in Nigeria employ the terms "first sleep" and "second sleep" to
refer to specific periods of the night
Source: Roger Ekirch
He attributes the initial shift to improvements in street lighting, domestic
lighting and a surge in coffee houses - which were sometimes open all night. As
the night became a place for legitimate activity and as that activity
increased, the length of time people could dedicate to rest dwindled.
In his new book, Evening's Empire, historian Craig Koslofsky puts forward an
account of how this happened.
"Associations with night before the 17th Century were not good," he says. The
night was a place populated by people of disrepute - criminals, prostitutes and
drunks.
"Even the wealthy, who could afford candlelight, had better things to spend
their money on. There was no prestige or social value associated with staying
up all night."
That changed in the wake of the Reformation and the counter-Reformation.
Protestants and Catholics became accustomed to holding secret services at
night, during periods of persecution. If earlier the night had belonged to
reprobates, now respectable people became accustomed to exploiting the hours of
darkness.
This trend migrated to the social sphere too, but only for those who could
afford to live by candlelight. With the advent of street lighting, however,
socialising at night began to filter down through the classes.
In 1667, Paris became the first city in the world to light its streets, using
wax candles in glass lamps. It was followed by Lille in the same year and
Amsterdam two years later, where a much more efficient oil-powered lamp was
developed.
London didn't join their ranks until 1684 but by the end of the century, more
than 50 of Europe's major towns and cities were lit at night.
Night became fashionable and spending hours lying in bed was considered a waste
of time.
Street-lighting in Leipzig in 1702 A small city like Leipzig in central Germany
employed 100 men to tend to 700 lamps
"People were becoming increasingly time-conscious and sensitive to efficiency,
certainly before the 19th Century," says Roger Ekirch. "But the industrial
revolution intensified that attitude by leaps and bounds."
Strong evidence of this shifting attitude is contained in a medical journal
from 1829 which urged parents to force their children out of a pattern of first
and second sleep.
"If no disease or accident there intervene, they will need no further repose
than that obtained in their first sleep, which custom will have caused to
terminate by itself just at the usual hour.
"And then, if they turn upon their ear to take a second nap, they will be
taught to look upon it as an intemperance not at all redounding to their
credit."
Today, most people seem to have adapted quite well to the eight-hour sleep, but
Ekirch believes many sleeping problems may have roots in the human body's
natural preference for segmented sleep as well as the ubiquity of artificial
light.
This could be the root of a condition called sleep maintenance insomnia, where
people wake during the night and have trouble getting back to sleep, he
suggests.
The condition first appears in literature at the end of the 19th Century, at
the same time as accounts of segmented sleep disappear.
"For most of evolution we slept a certain way," says sleep psychologist Gregg
Jacobs. "Waking up during the night is part of normal human physiology."
The idea that we must sleep in a consolidated block could be damaging, he says,
if it makes people who wake up at night anxious, as this anxiety can itself
prohibit sleeps and is likely to seep into waking life too.
Continue reading the main story
Stages of sleep
Every 60-100 minutes we go through a cycle of four stages of sleep
Stage 1 is a drowsy, relaxed state between being awake and sleeping - breathing
slows, muscles relax, heart rate drops
Stage 2 is slightly deeper sleep - you may feel awake and this means that, on
many nights, you may be asleep and not know it
Stage 3 and Stage 4, or Deep Sleep - it is very hard to wake up from Deep Sleep
because this is when there is the lowest amount of activity in your body
After Deep Sleep, we go back to Stage 2 for a few minutes, and then enter Dream
Sleep - also called REM (rapid eye movement) sleep - which, as its name
suggests, is when you dream
In a full sleep cycle, a person goes through all the stages of sleep from one
to four, then back down through stages three and two, before entering dream
sleep
Source: Gregg Jacobs
Russell Foster, a professor of circadian [body clock] neuroscience at Oxford,
shares this point of view.
"Many people wake up at night and panic," he says. "I tell them that what they
are experiencing is a throwback to the bi-modal sleep pattern."
But the majority of doctors still fail to acknowledge that a consolidated
eight-hour sleep may be unnatural.
"Over 30% of the medical problems that doctors are faced with stem directly or
indirectly from sleep. But sleep has been ignored in medical training and there
are very few centres where sleep is studied," he says.
Jacobs suggests that the waking period between sleeps, when people were forced
into periods of rest and relaxation, could have played an important part in the
human capacity to regulate stress naturally.
In many historic accounts, Ekirch found that people used the time to meditate
on their dreams.
"Today we spend less time doing those things," says Dr Jacobs. "It's not a
coincidence that, in modern life, the number of people who report anxiety,
stress, depression, alcoholism and drug abuse has gone up."
So the next time you wake up in the middle of the night, think of your
pre-industrial ancestors and relax. Lying awake could be good for you.