Sleep Facts



  • When you are asleep, many of your body functions go on as normal — even your brain goes on receiving sense signals. But your body may save energy and do routine repairs.
  • Lack of sleep can be dangerous. A newborn baby needs 18 to 20 hours sleep a day. An adult needs around 7 to 8.
  • Sleep is controlled in the brain stem (see the brain). Dreaming is stimulated by signals fired from a part of the brain stern called the pons.
  • When you are awake, there is little pattern to the electricity created by the firing of the brain’s nerve cells. But as you sleep, more regular waves appear.
  • While you are asleep, alpha waves sweep across the brain every 0.1 seconds. Theta waves are slower.
  • For the first 90 minutes of sleep, your sleep gets deeper and the brain waves become stronger.
  • After about 90 minutes of sleep, your brain suddenly starts to buzz with activity, yet you are hard to wake up.
  • After 90 minutes of sleep, your eyes begin to flicker from side to side under their lids. This is called Rapid Eye Movement (REM) sleep.
  • REM sleep is thought to show that you are dreaming.
  • While you sleep, ordinary deeper sleep alternates with spells of REM lasting up to half an hour.