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August 02, 2021

A guide to understanding each stage of sleep

Adult Health Sleep

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You spend a third of your life asleep. You know what you’re doing during those waking hours, but when you nod off for the night, what happens? Maybe you wake up with a vague memory of a dream, but there’s so much more going on overnight than that.

Each night, you cycle through four different stages of sleep several times — REM (Rapid Eye Movement) and three stages of non-REM sleep. Here’s what happens in each stage.


Stage 1: When you first begin to doze off, your body experiences a few minutes of transitioning from wakefulness to sleep as your brain waves begin to slow down from their waking patterns. This is very light sleep, and it’s when your heartbeat, breathing, and eyes relax. Some people experience muscle twitches as their body slows down and prepares for rest and sleep.

Stage 2: As you fall asleep, your body enters a period of light sleep. This transitionary period occurs as your body continues to relax even further. In addition to more relaxed muscles and slower breathing and heartbeat, body temperature drops, and eye movements stop.

Stage 3: To feel refreshed each morning, your body needs deep sleep. At this point of sleep, your body is at its most relaxed, making it more difficult to be woken up. During this sleep stage, your body releases hormones, performs tissue growth and repair, and restores energy.

REM Sleep

After about 90 minutes of sleep, you may experience your first period of rapid eye movement; your eyes begin moving quickly behind your closed eyelids, and brain activity increases to be closer to what it is when you are awake. Breathing, heart rate, and blood pressure all reach similar levels, and your arm and leg muscles are temporarily paralyzed. It’s a common myth that you only dream during REM sleep. While most dreaming does occur during that stage, you can dream in any sleep stage.

During a normal night of sleep, you will cycle through each of these stages several times. Although you spend more time in stage 2 than any other stage, your body experiences longer periods of stage 3 sleep in the first half of the night, and longer, deeper periods of REM sleep as morning approaches. The amount of time you spend in REM sleep declines as you get older.

A good night’s sleep is critical for your health. To ensure you sleep well each night, make it a point to go to bed and wake up around the same time each day. You should also avoid caffeine before you sleep, and instead, relax. Lying in bed awake watching TV or using your mobile devices should be avoided as well — keep your bed sacrosanct as a place for sleep!

When you wake up in the morning, you’ll likely only remember a small portion of the dreams you had — but now you’ll know everything your body was experiencing during each of the four stages of sleep.

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