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The importance of rapid eye movement (REM), non-REM and how they affect your sleep

starry dark sky with clock and the words "REM Sleep"

Why is sleep important to your health?

Scientists say that a good night’s sleep is as important to survival as food and water. If you don’t get enough sleep, it makes it difficult to concentrate and control your focus when you need it the most. 

Too little sleep can also put you at risk of health problems such as high blood pressure, depression and obesity. Needless to say, sleep affects every part of the body. And getting an adequate amount and quality of your sleep is crucial to keep everything running smoothly. 

There are two main types of sleep that contribute to proper rest — rapid eye movement (REM) and non-REM cycles. Both serve a special function, though people are often more familiar with the REM cycle. 

Before REM begins

The REM cycle takes place after the non-REM cycle. So, what is non-REM sleep? It’s the initial part of sleep that occurs from the time you drift off until the point where you reach a deep state of unconsciousness. 

During this time, motions within your eyes are slow and come to a stop at a certain point. That’s why this segment is referred to as non-rapid eye movement (non-REM) sleep.

The non-REM cycle includes the following stages:

  • Stage 1 — The first stage of non-REM involves a transition from being awake to drifting into a light sleep. This stage lasts several minutes as your heart rate, eye movements and breathing slow down. Your muscles also relax and your brain activity eases up.

  • Stage 2 — Your body remains in a light sleeping state as your breathing and heart rate slow even more. Muscles also relax more as your body temperature drops and your eyes stop moving. 

  • Stage 3 — In stage 3 of non-REM sleep, your breathing and heartbeat sink to their lowest rates. This is the stage that gives you that fully rested feeling the next day. 

Throughout the night, your body cycles through each of the stages of both non-REM and REM sleep. You spend the most time in stage 2 of non-REM sleep. 

What is REM sleep?

The rapid eye movement (REM) cycle of sleep is the second part of the overall sleep sequence, following each stage of non-REM. 

When signals are sent to the cerebral cortex of the brain, the REM cycle is triggered. The majority of dreaming takes place during this time, as the cerebral cortex is the part of the brain where thinking and learning occur.

The cerebral cortex is also the part of the brain that is used for storing information and memories. Experts say that if you miss out on REM sleep, your memory may be affected. 

When you get older, your body spends less time in the REM cycle each night.

SEE RELATED: Obstructive sleep apnea and how it can affect your eyes 

What happens during REM sleep?

During the REM sleep stage, your body experiences several new sensations, including the following:

  • Your eyes move quickly from side to side beneath closed eyelids (hence the name “rapid eye movement”)

  • Blood pressure and heart rate increase

  • You begin to breathe faster and at an irregular rate

  • Your muscles fall into a paralyzed-like state

  • Brain waves increase 

When does REM start and how long does REM sleep last?

REM begins approximately 90 minutes into your sleeping timeline. The first sequence of REM sleep lasts up to 10 minutes — and the ending sequence can last up to an hour. 

Throughout the night, you cycle through each stage of both non-REM and REM sleep between four and six times.

Up to 25% of your time sleeping is spent in the REM cycle (75% of which is spent between each stage of the non-REM cycle).

Why do our eyes move in REM sleep?

New research suggests that every time a person’s eyes move while they’re asleep, that person is processing a new visual message in their dream. 

Scientists at Tel Aviv University conducted a study to determine the relationship between the brain’s neurons and rapid eye movement during sleep. They concluded that eyes move as they process new visual information — and move rapidly during the cycle of sleep that involves visual dreaming. 

The data suggest that visual processing in the brain is similar in both conscious and unconscious states.

Did you know? The eyes and diaphragmatic muscles are the only parts of the body that move during REM sleep — the rest of your muscles act as though they are paralyzed during this time.

SEE RELATED: Your eyes while sleeping: Moving, twitching, rolling and more 

Getting a good night’s rest

REM sleep is very important to your health. It contributes to your mood and concentration levels. It also encourages your brain to collect and store new information, improving your memory. Additionally, REM sleep supports your immune system and healthy cell growth. 

Try the following tips to wind down and get the best out of your slumber:

  • Turn off electronics one to two hours before bedtime.

  • Limit the amount of caffeine and alcohol you consume. 

  • Nourish your body with moderate exercise.

  • Establish a routine and try to go to bed at the same time every night.

  • Relax your body before bed with activities such as yoga, reading, taking a bath or listening to music.

  • Try wearing a sleep mask to block excess light from your eyes.

Sleeping troubles can be irritating and tiresome (literally). Talk to your doctor if you experience problems falling asleep or staying asleep, or if you struggle to stay awake during the day.

READ NEXT: The harmful effects of sleep deprivation

Brain basics: Understanding sleep. National Institute of Neurological Disorders and Stroke. July 2022. 

What happens during sleep? Eunice Kennedy Shriver National Institute of Child Health and Human Development. April 2019.

Physiology, sleep stages. StatPearls. April 2022.

Scientists have worked out why your eyes move when you're dreaming. Science Alert. August 2015.

Single-neuron activity and eye movements during human REM sleep and awake vision. Nature Communications. August 2015.

What is REM Sleep? National Sleep Foundation. November 2020.

Systematic review of light exposure impact on human circadian rhythm. Chronobiology International. February 2019.

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