All human beings follow similar sleeping patterns. One sleep cycle is 90 to 110 minutes. A typical night’s sleep is the repetition of this cycle. There are four stages of sleep.

Stage 1 – Stage one sleep is the lightest of the four stages where the brain wave patterns are similar when we are awake. The body is very active during this stage. The brain temperature rises, blood pressure and pulse rate fluctuates, breathing is irregular and the brain consumes more oxygen. We have several stage 1 sleep periods during a night.

Stage 2 – Stage 2 sleep begins usually within the first 5 to 10 minutes. This is the period where sleep-talking takes place. Stage 2 sleep becomes shorter and shorter with each sleep cycle.

Stage 3 – In stage 3 sleep the breathing is slow and even, the pulse rate has slowed down and the body temperature has dropped. During this period the brain produces five times more electricity as when we are awake. During this stage it is difficult to awake a person. This is the time when most dreaming happens. During this period the body has almost shut down and the brain sends messages to the spinal cord to suppress muscle activity. This is the reason why people cannot run or cry out during a nightmare. In the beginning stage 3 sleep lasts 10 to 15 minutes, but at the end of the night it can last 40 to 60 minutes in a cycle. With each cycle stage 3 sleep time increases.

Stage 4 – Stage 4 sleep is the deepest level of sleep. In the first cycle this will be usually 20 minutes or more. Stage 4 becomes shorter and shorter during the sleep and before the end of the sleep there is no stage 4 sleep in the cycle.

In stage 4 sleep only the growth hormones are released into the body and so teenagers need more of this than adults.

People over 70 may have almost no stage 4 sleep in their sleep cycle. This is the reason why they do not have sound sleep. This makes them sick.