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What Does REM Stand For?

Lara Vargas


REM, which stands for Rapid Eye Movement, is the final stage in the sleep cycle, marked by rapidly-shifting eyes. REM sleep is the closest stage to wakefulness, as our brain’s activity levels are heightened; and during this sleep stage, we can experience very vivid dreams.

In this article, we discuss the various stages of sleep and their characteristics, as well as the impact REM sleep has on our overall health and wellbeing.

Understanding the Stages of Sleep

There are two types of sleep that occur during a typical night of rest: Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep, and NREM sleep is broken into various stages. During a night of sleep, you will cycle through the four phases multiple times—usually, adults complete 5 to 7 sleep cycles each night.

Each stage of sleep plays an important role in our quality of rest and is marked by distinct changes in our brain and body.

NREM Sleep

NREM sleep consists of the first three stages of sleep we experience. Each stage varies in length and has unique characteristics.

Stage 1

The first stage consists of our transition from wakefulness to sleep. It lasts only a few minutes, during which our heart rate, breathing, and eye movements slow down. Muscles begin to relax and may twitch, and our brain waves begin to slow as well. It’s fairly easy to wake someone up who’s in NREM Stage 1 because it’s very light sleep.

Stage 2

During the second phase of sleep, our heart rate and breathing slow down even more while our muscles further relax. Eye movement stops and our body temperature drops. While our brain wave activity continues to slow, it can experience bursts of activity. This stage of sleep can last anywhere from 30 to 60 minutes.

Stage 3

Also known as deep sleep or slow-wave sleep, NREM Stage 3 lasts between 20 and 40 minutes and is the stage that makes us feel refreshed and rejuvenated when we wake up. In this phase, our heart rate and breathing slow to the lowest levels, and our brain waves slow down even more. Muscles are fully relaxed in this sleep stage, and it can be rather difficult to wake someone up when they’re in deep sleep.

REM Sleep

After progressing through the three stages of NREM, we enter REM sleep. Usually, we reach this phase about one to two hours after falling asleep. During this stage, our brain wave activity becomes very active with fast, desynchronized patterns, and reaches levels close to wakefulness. Our body also experiences physiological changes that are similar or close to being awake. Common changes during REM sleep include:

  • Fluttering eyes and eyelids
  • Fast and irregular breathing
  • Heart rate and blood pressure increase
  • Body temperature change
  • Increased oxygen consumption by the brain

REM sleep is the stage where most of our dreaming occurs because of our heightened brain activity. During REM, our brain temporarily paralyzes our muscles (known as atonia) in order to prevent us from acting out our dreams. A person woken up in the REM sleep stage can usually recall their dreams easily. Since our brain is active but our muscles are paralyzed, REM sleep is sometimes referred to as paradoxical sleep.

After REM, a person will start the sleep cycle over, repeating it three to four times a night. The time spent in REM progressively increases with each cycle, with the longest period of REM sleep happening during the final hours of sleep (usually early in the morning for most people) and lasting roughly one hour.

The Importance of REM Sleep

Every stage in the sleep cycle is important for our health and REM sleep benefits us both mentally and physically.

Aids in Brain Development

A Washington State University study suggests that REM sleep is vital in developing the brain, especially in younger children. The study found that animals deprived of REM sleep showed abnormal brain development. Those deprived of NREM sleep, on the other hand, did not show any abnormalities.

This could explain why infants spend up to 70 percent of their sleep time in the REM phase. And, as we get older, our time spent in REM sleep decreases with adults spending about 20 percent of their sleep in the REM phase.

Improves Memory and Learning Skills

Even in our adult years, REM sleep still plays an important role in brain function. One study revealed the effects REM sleep has on our cognitive abilities. During the study, a group of people was taught a skill before falling asleep. One group was then deprived of REM sleep while the other was deprived of NREM sleep. The group deprived of REM sleep had a much more difficult time recalling what they were taught than those deprived of NREM sleep.

The Mayo Clinic states that REM sleep is the stage of sleep when our brains sort important information from unimportant information. During this phase of sleep is also when we convert short-term thoughts into long-term memories. When we don’t get enough REM sleep, our mental focus and acuity may suffer, and we may even feel short-tempered and cranky.

Improves Our Ability to Process Emotional Experiences

REM sleep has also been proven to help us better process emotional or stressful events. Researchers at UC Berkeley found that during REM sleep our stress chemistry shuts down and the brain is able to process emotional experiences. When our brains can process these events during this “safe” phase, we wake up feeling less emotional and more rational about these experiences.

Supports Healthy Weight

Getting enough REM sleep is important for maintaining a healthy weight. The Mayo Clinic conducted a study that revealed a link between leptin, a hormone that regulates appetite, and sleep stages including REM. It found that those experiencing more REM sleep had a greater decrease in leptin.

Another study on the relationship between REM sleep and appetite suggests that not getting enough REM sleep may enhance appetite and contribute to weight gain through overeating, especially in habitually short sleepers.

Sleep Disorders Affecting REM Sleep

There are many different sleep disorders and some of them directly affect the REM sleep stage. It’s important to recognize the symptoms of these disorders because they can sometimes be misdiagnosed as other conditions.

REM Sleep Behavior Disorder

REM Sleep Behavior Disorder (RBD) is a condition affecting nerve pathways in the brain that prevent muscles from moving during REM sleep. Typically we experience muscle atonia during REM, which is a loss of muscle tone that temporarily paralyzes our arms and legs. This is important for keeping us from acting out our dreams.

In someone with RBD, these nerve pathways no longer work and they may physically act out their dreams. Symptoms of this can include movement like kicking, punching, or even jumping from the bed. It can also include noises like talking, laughing, and shouting, all in response to the dream. Episodes may happen occasionally or up to several times a night. This can potentially cause injury and distress to those with RBD and any sleeping partners.

RBD generally worsens with time and is usually gradual in developing. It’s often an early sign of a neurodegenerative disorder like Parkinson’s, dementia with Lewy bodies, and multiple system atrophy. In fact, 81 to 90 percent of people with RBD end up developing a neurodegenerative disorder.


Narcolepsy is a neurological disorder affecting the brain’s ability to control the sleep-wake cycle. In a typical sleep cycle, it takes anywhere from one to two hours to enter REM sleep. In someone with narcolepsy, they often enter the REM stage quickly, after about just 15 minutes.

Symptoms of narcolepsy include excessive daytime sleepiness (EDS), sleep paralysis, hallucinations, temporary or fragmented sleep episodes, and insomnia. It can also include cataplexy, a loss of muscle tone while a person is awake. Similar to the muscle paralysis that happens during REM that prevents us from acting out our dreams, cataplexy can cause the entire body to collapse and is often mistaken for a seizure.

It’s not entirely clear what causes narcolepsy but there could be multiple factors including low levels of hypocretin. This naturally occurring chemical is responsible for promoting wakefulness and regulating REM sleep.

While narcolepsy is a chronic disorder, it doesn’t usually get worse over time and sometimes symptoms can even slightly improve.

How to Improve REM Sleep

We know that simply getting more sleep will ensure we experience more REM sleep. To achieve deeper sleep, try some of these simple tips:

  • Stick to a sleep schedule: Aim to go to bed and wake up at the same time each day, even on the weekends. This consistency will reinforce your natural sleep-wake cycle and lead to better quality sleep.
  • Maintain healthy eating habits: Avoid eating heavy or large meals right before bed since these can make you feel uncomfortable and keep you awake longer. Instead, try eating foods to promote better sleep at dinnertime.
  • Create a restful environment: A cool, dark, and quiet environment encourages rest and relaxation.
  • Limit daytime naps: Naps can interfere with your sleep schedule. However, if you must nap, do so earlier in the day and for no longer than 30 minutes.
  • Exercise regularly: Physical activity can promote better sleep and overall health.
  • Manage stress: Learn to manage stress and worry since both can keep you up late at night.


Is REM sleep the same as deep sleep?

REM sleep and NREM Stage 3 are often considered to be “deep sleep,” but the deepest sleep actually occurs in NREM Stage 3. Our brain is at its most active state during REM sleep—brain activity during REM sleep is actually similar to that when we’re awake, making Stage 3 the deepest stage of sleep.

Deep sleep takes place just prior to entering REM, in the third stage of NREM sleep. During this phase, our brain waves slow down considerably, and our heartbeat and breathing slow to the lowest levels. Muscles become very relaxed and it’s usually challenging to wake someone from this phase. NREM Stage 3 is where we experience the most rejuvenating sleep.

What stage of sleep do you dream in?

You can dream in any stage of sleep but it most often happens during REM. Since our brain waves are at their most active during this stage, we usually experience very vivid dreams. Someone who is woken up during REM can typically remember their dreams, whereas it can be more difficult to recall dreams when woken up during other stages of sleep.

Why is REM sleep important?

REM sleep plays an important role in brain health. Research shows REM sleep is vital for developing young brains and improving memory and learning skills in adults’. REM is when our brains sort information and convert thoughts into memories. REM sleep has also been proven to provide a “safe space” for our brains to process emotional events. In turn, we’re able to more rationally handle these events when we’re awake.

Getting enough REM sleep is also important for maintaining healthy eating habits because there is a direct link between it and the hormone leptin, that regulates appetite. Without enough REM sleep, there’s a decrease of leptin and we’re more likely to overeat.

What happens during REM sleep?

We are closest to wakefulness during REM sleep and we experience physical and mental changes. The most obvious one is rapid eye movement, where the eyes quickly move back and forth while closed. Breathing quickens and heart rate and blood pressure increase. During REM, our brain wave activity is at its highest in the sleep cycle and we generally experience dreams with vivid imagery.

What does it mean if I act out my dreams?

If you act out your dreams, it could mean that you’re suffering from REM Sleep Behavior Disorder (RBD).

Typically during REM, when our dreams are most vivid, we experience a loss of muscle tone called atonia. When this happens, we become temporarily paralyzed, preventing us from physically acting out our dreams. Nerve pathways in our brains are responsible for making this happen. However, in someone with RBD, these pathways stop working, allowing them to move around during REM.

It’s important to speak with a doctor if you think you may be suffering from RBD. The condition is often the first sign in people who eventually develop neurodegenerative disorders and it can worsen over time.


Without getting enough sleep, we are unable to reap the full benefits of each stage. During Rapid Eye Movement sleep, which is the final phase in the cycle, our brain’s activity level is at its highest and is when we sort information, convert thoughts into memories, and process emotions. It’s also a crucial stage for young brain development.

REM sleep is when we are closest to wakefulness and the stage where we dream the most. When we are in REM, our bodies experience many changes including temporary paralysis, but some sleep disorders like REM Sleep Behavior Disorder and narcolepsy can affect this temporary paralyzation and can be dangerous if not treated.

To ensure we experience more REM sleep, it’s important to get the recommended seven hours of sleep each night. We can do this by striving for healthy sleep habits, like sticking to a consistent schedule and eliminating blue light before bed.

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