Which Sleep Stage is Most Important?   

Which Sleep Stage is Most Important?

Woman sleeping in a bed

February 08, 2023

Clinical Contributors to this story:
Georges Ghacibeh, M.D.

Throughout a night of sleep, there are four different stages of sleep. Neurologist and sleep medicine expert, Georges Ghacibeh, M.D., explains what happens during each stage and which is most crucial to feeling rested. 

While all the stages of sleep are important to the cycle, stage 3 is the deepest, most restful sleep. During this stage, your body releases hormones that help repair muscles, bones and tissues, and your brain works on consolidating your memories,” says Dr. Ghacibeh. 

“You should get about seven to nine hours of sleep a night, during which your brain will cycle several times through light sleep, deep sleep, and dream or REM sleep,” explains Dr. Ghacibeh. 

Light Sleep 

Stage 1:

  • In stage one of sleep, a person will transition between drowsiness and wakefulness.
  • Average duration: 1 to 5 minutes

This is non-rapid eye movement (NREM) sleep, a light sleep stage where you will relax and perhaps twitch as you slowly drift into stage two of sleep. 

Stage 2:

  • In stage two, you remain in light sleep, but your body and muscles will relax. 
  • Average duration: 10 to 60 minutes

Heartbeat, breathing, and brain waves all slow down. Sleep becomes more regular during this stage.

Deep Sleep

Stage 3: 

  • This is the deepest stage of sleep and tends to happen earlier in the night. 
  • Average duration: 20 to 60 minutes

The body becomes so relaxed that it can be very difficult to awaken. This stage is called the “healing stage” because the body does essential tissue growth and repair. Hormones are released and cell energy is renewed, and memories learned during the day are consolidated in the brain. 

Stage 4 - REM Sleep: 

  • REM sleep is where dreaming is most likely to occur.
  • Average duration: A person will enter REM sleep around 90 minutes after they have fallen asleep, and REM will reoccur every 90 minutes during sleep. 

During this sleep stage the eyes may move in random directions while the lids are closed (Rapid Eye Movements). The brain waves look almost as if the person is awake, and breathing, heart rate, and blood pressure increase and decrease randomly, says Dr. Ghacibeh. Arms and legs become temporarily paralyzed to block one from physically performing their dreams. 

REM sleep generally takes up about a quarter of sleep. But there is no official scientific consensus on how much REM sleep an individual should get. 

“Many people wake up tired, even with adequate amounts of sleep. This is likely due to insufficient amounts of deep and REM sleep” shares Dr. Ghacibeh. “So while all stages of sleep are essential to overall well-being, deep sleep is considered the most important stage.”

Next Steps & Resources:

The material provided through HealthU is intended to be used as general information only and should not replace the advice of your physician. Always consult your physician for individual care.



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