I found this very interesting article about sleep online (here is a slightly abbreviated version.)
The myth of the eight-hour sleep
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.
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.
[The
article gives examples of segmented sleep references from literature]
- "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
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.
A small city like Leipzig in central
Germany employed 100 men to tend to 700 lamps.
"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.
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
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.
......Very interesting article, I had never heard of segmented sleep until I read this.
A Votre Sante (Here's To Your Health,) Alix
