"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.
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.
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.
"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.
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."
