Updated 31 January 2011

Interesting facts about sleep

For seven or eight hours per day, we go into a profoundly different state – a system – shutdown, if you will. But how much do you really know about sleep?


For seven or eight hours per day, we go into a profoundly different state – a system – shutdown, if you will. But how much do you really know about sleep, about why we need it and what happens while we have our nightly shuteye?

See how many of the following facts you knew:

  • During a normal night's sleep, there are five different stages of sleep – and each of them is quite different from the other four.
  • When we are sleeping deeply, our breathing, our heart rate and blood pressure reach their lowest levels of the day.
  • While we are dreaming, we experience REM – rapid eye movement. This is a very active time for both the body and the brain.
  • While we are dreaming, our brain patterns are similar to those we experience while being awake.
  • Most adults need about eight hours of sleep to function at their best, but studies have shown that most adults don't get much more than seven.
  • We sleep more lightly during the second half of the night than during the first.
  • Cats sleep up to 18 hours a day.
  • Your body is on a 24-hour body clock, which makes you wind down between 1 am and 6 am and again in the three hours directly after lunch. We are really made to have siestas.
  • It is more difficult to wake a child than an adult from deep sleep – often children will be disorientated and have no recollection of this later.
  • Many people who suffer from insomnia suffer from anxiety and depression.
  • Our large body muscles are paralysed while we sleep – most probably to stop us from doing what we are dreaming about.
  • We go through four to six sleep cycles during a good night's sleep, moving through the different stages and back again.
  • The average person wakes up about six times per night.
  • Your body temperature falls in the early morning hours, reaches a low at about 4 a.m. and then rises again just before sunrise.
  • Researchers have never been able to agree exactly why the body needs sleep, except that it is restoring to our bodies and our brains.
  • Even when we are sleeping very deeply, there is still a part of us that picks up sounds and signals from the world around us. That's why parents wake up when the baby cries, but they don't hear the howling southeaster.
  • Women and older people most often suffer from insomnia.

QUIZ: are you sleep-deprived?

The Sleep Condition Centre

(Sources: Health24,

(Health24, updated January 2011)


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