What Is REM Sleep And Why Does It Matter?

Fact Checked Medically reviewed by Tanja Premru-Sršen


“If you can’t sleep, then get up and do something instead of lying there worrying. It’s the worry that gets you, not the lack of sleep.” — Dale Carnegie, American Writer

Sleep is one of the most important parts of our daily lives. It is important for optimal function and good health.

Our body goes through various sleep cycles when we get our much-needed, revitalizing rest at night.

Each sleep cycle and phase is beneficial for our mind and body, but REM is especially fascinating. REM sleep promotes learning, increases brain activity, and creates dreams.

Before diving into what is REM Sleep, first, we need to discuss the three stages of N-REM Sleep and REM Sleep.

Difference Between REM And Non-REM Sleep

When we sleep at night, our body goes through periods of REM and NREM Sleep. Non-REM sleep occurs in three stages after which our body enters the REM Sleep stage.

Non REM Sleep

The three phases of Non-REM Sleep are:

  • PHASE 1 OF NON REM SLEEP:As we first drift off to sleep we enter phase 1 of Non REM Sleep. We become relaxed but may wake up easily or stir for ten to fifteen minutes.
  • PHASE 2 OF NON-REM SLEEP:Phase 2 of Non-REM sleep prepares our body for deep sleep. Our heart rate and body temperature begins to lower down as we begin to sleep.
  • PHASE 3 OF NON REM SLEEP:Deep sleep begins in Phase 3 of N-REM Sleep. During stage 3 of Non-REM sleep, we cannot be woken up easily as our body works to repair bones and tissues and strengthen the immune system.

REM Sleep

REM’s full form is Rapid Eye Movement. During this cycle of sleep, our eyes will move and dart quickly beneath the eyelids and we experience rapid eye movement.

During REM sleep, our brain activity increases, our pulse quickens and we experience dreams.

We first enter REM sleep 90 minutes right after we fall asleep. The first REM sleep cycle lasts 10 minutes and each cycle time gradually increases to as long as one hour in the last phase before we wake up.

What Is The Importance Of REM Sleep?

Although all cycles of sleep are important, REM Sleep, in particular, plays an important role in memory, dreaming, emotional processing and proper brain development.

Memory Consolidation

During REM Sleep, our brain processes new motor skills and learnings from the day, committing some to our memory, maintaining others, and deciding which ones to delete.

A part of memory consolidation also takes place in deep sleep which is a non-REM stage.


Most of our dreams take place during the REM Sleep phase. However, REM Sleep is not the time we experience dreams.

The dreams that you experience in REM Sleep are much more vivid than in N-REM Sleep.

Emotional Processing

Our brains tend to process emotions during the REM Sleep stage. Dreams which are more vivid in REM Sleep are involved in emotional processing.

Our amygdala, the part of our brain that processes emotions also gets activated during the REM Sleep.

Brain Development

Research suggests REM Sleep promotes brain development since most newborns experience sleep in the REM sleep stage.

More evidence also tells us that animals born with less developed brains, such as human babies and puppies spend more than 80% of their sleep time in the REM sleep cycle.

Wakefulness Preparation

REM Sleep activates our central nervous system, which helps us to get ready to wake back up.

This explains why we spend an increasing amount of time in REM sleep as the night progresses and why we find it easier to wake up during this stage.

How Much REM Sleep Does A Person Need?

We need the most REM Sleep as children and infants as this is when our brain is most developing.

Newborn babies tend to spend eight hours of REM sleep every day. By adulthood, we only need an average of two hours of REM Sleep every night.

Our bodies alter our REM sleep duration both from day to day and over the course of our lives according to our physical and biological needs.

Similarly, the time spent in certain stages of sleep, including the REM sleep stage, varies from night to night depending on what our body needs.

What Happens If We Do Not Get Enough REM Sleep?

Multiple studies both on humans and animals suggest that not getting enough REM Sleep interferes with memory formation.

However, memory problems usually associated with low levels of REM Sleep could be due to overall bad sleep quality, since these often occur together.

In other words, REM Sleep deprivation disrupts our brain’s natural ability to generate new cells.

Without adequate REM sleep, our cognitive performance declines gradually. We may find ourselves forgetting things more often, as our working memory gets highly affected by sleep deprivation.

Short sleepers or those who experience light sleep go through the same impairments to their brain as someone who has not slept for two nights in a row.

Since we get most of our REM Sleep in the latter part of the night, people who sleep lightly spend less time in REM Sleep.

Sleep Disorders Associated With Abnormal REM Sleep

Certain sleep disorders get associated with abnormal REM Sleep.

These include REM Sleep behaviour disorder, nightmare disorder and narcolepsy.

REM Sleep Behavior Disorder

People with REM Sleep Behavior Disorder or RBD do not experience muscle paralysis during REM Sleep, so they may act out of their dreams.

They may punch, kick, shout, or jerk in their sleep which leads to them injuring not only themselves but also their sleeping partner.

This disorder is caused by a breakdown in the brainstem area responsible for regulating REM Sleep. Often times it precedes the development of a neurodegenerative disease.

Nightmare Disorder

Nightmares mainly occur during REM Sleep. A person with nightmare disorder regularly experiences distressing, intense and frightening dreams.

Such dreams are often caused by childhood trauma, stress, and other frightening experiences.

Other REM Sleep disorders

  • Narcolepsy
  • Obstructive Sleep Apnea  and Central Sleep Apnea
  • Other neurological disorders such as Parkinson’s Disease

When You Should Visit A Doctor?

The risk factors involved with not getting enough REM Sleep are not only detrimental to the person suffering but also to those around them.

If a person notices symptoms of sleep deprivation or believes that they might have a sleep disorder such as REM sleep Behavior Disorder or nightmare disorder, then they should get in touch with a doctor.

Doctors and sleep specialists help in determining the cause of our REM sleep issues and develop a strategy to improve our REM sleep quality.