What happens during a typical nights rest

February 09, 2001

What happens during a typical night's rest?

Marc Key, supervisor at Sleep Disorders Center of Western Maryland, says these are the five stages of sleep people enter during a typical night's rest:

Stage 1 - A transitional stage between being awake and falling asleep. When hitting the snooze bar, people usually fall into Stage 1 sleep before entering Rapid Eye Movement (REM) sleep.

Stage 2 - Called True sleep, it is where most people spend the majority of their night. Between 50 percent and 55 percent of their sleep is True sleep.

Stage 3 and Stage 4 - Grouped together, they are called Delta sleep.

"If you consider your body is like two batteries, (Delta sleep) is where it recharges your physical being," Key says.

When you are sick or have spent a long day exercising and taxing muscles, this is the sleep stage where the body fixes itself. In children and adolescents, growth hormones are released while they are in Delta sleep.


People spend between 20 percent and 25 percent of their night in Delta sleep.

Rapid Eye Movement (REM) - The stage of sleep where people dream.

If Delta sleep rejuvenates the body, REM sleep revitalizes the mind, Key says. Over time, not getting enough REM sleep can contribute to such conditions as depression or impotence.

"It throws everything off kilter," Key says about not getting enough REM sleep. "Because that's where the psychological part of you rejuvenates itself."

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