Rapid eye movement (REM) sleep is one of four stages the brain moves through while sleeping. In REM sleep, the eyes move rapidly in various directions and dreams can occur. REM sleep typically starts within 90 minutes of falling asleep.

People typically enter REM sleep within the first 90 minutes of falling asleep. As the sleep cycle repeats, REM sleep occurs several times while a person is resting. In fact, it accounts for approximately 20–25% of an adult’s sleep cycle and over 50% of an infant’s.

Most dreams occur during REM sleep. This is a stage that may play a role in learning, memory, and mood.

This article covers REM sleep in more detail, including its stages, functions, and more.

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REM sleep typically starts within 90 minutes of a person falling asleep, and it cycles around every 90 minutes.

During REM sleep, the body and brain go through several changes, including:

Most people experience a state of temporary paralysis as the brain signals the spinal cord to cease the movement of the arms and legs.

This lack of muscle activity is known as atonia, and it may be a protective mechanism to prevent injury that may result from “acting out” our dreams.

During REM sleep, people may experience vivid dreams due to the increase in brain activity.

Before entering the REM sleep phase, the body goes through each of the stages of non-REM sleep. The sections below look at each of these in more detail.

Stage 1 non-REM sleep

A person in this stage is between being awake and asleep or is in a state of very light sleep.

Stage 2 non-REM sleep

A slightly deeper sleep characterizes this stage. Body temperature drops, and heart rate slows down. Most people spend around half of their total sleep time in this stage.

Stages 3 non-REM sleep

Stage 3 non-REM sleep is a state of deep and restorative sleep known as slow-wave sleep or delta sleep. The muscles relax, the supply of blood to the muscles increases, and the body repairs and grows tissue.

REM sleep

People enter the REM sleep phase following the above stages. This is the stage of sleep during which most people dream, though this may also happen in non-REM sleep.

REM sleep may benefit learning, memory, and mood. A lack of REM sleep may have adverse implications for physical and mental health.

Learning and memory

The brain processes information and consolidates memories during sleep. As a result, sleep deprivation can negatively affect a person’s working memory.

A 2016 study involving healthy adolescents also found that sleep deprivation could increase the risk of forming false memories.

According to some studies, even short periods of daytime sleep can help a person learn muscle patterns (motor memory) and commit them to memory.

Central nervous system development

REM sleep may be essential for brain development in infants. Some research indicates that this sleep stage is responsible for the neural stimulation necessary for mature brain structure developments.

These findings may help explain why infants require higher levels of REM sleep, with the number of minutes of REM sleep falling as people age.

Consequences of a lack of REM sleep

Some studies link a lack of REM sleep to:

  • Reduced coping skills: Some research suggests that a lack of REM sleep may reduce a person’s ability to differentiate between threatening and non-threatening stimuli and respond accordingly.
  • Migraine: Fragmented sleep may increase a person’s risk of experiencing migraine in the immediately following days. However, low sleep duration and quality did have an effect on migraine rate.
  • Obesity: Some studies associate the quantity and quality of sleep with an increased chance of obesity.

Drinking alcohol before sleep can disrupt a person’s sleep cycle and sleep quality. Research is conflicting on how exactly alcohol affects REM sleep.

Several studies report that alcohol intoxication does not reduce overall REM sleep but does reduce overall sleep quality. However, a further review of historic sleep research found several instances in which the duration and quality of REM sleep were lower following alcohol intoxication.

Alcohol affects sleep in other ways, too. For example, it contributes to sleep apnea and snoring, causes an increase in bathroom visits, and interrupts the body’s circadian rhythm, which is the internal clock that regulates sleep and wake times.

Some people experience REM sleep behavior disorder (RBD). This is a condition wherein the muscle paralysis a person usually experiences during REM sleep does not occur. It causes the person to act out vivid dreams. For example, they may kick, yell, or flail their arms.

The onset of RBD tends to be gradual, with symptoms worsening over time.

RBD results from malfunctioning nerve pathways in the brain. Some risk factors for its development include:

  • being male
  • being over 50 years old
  • taking antidepressants
  • experiencing withdrawal from drugs or alcohol
  • having a neurodegenerative condition, such as Parkinson’s disease
  • having narcolepsy, which is a sleep disorder characterized by excessive daytime sleepiness and hallucinations

Treatment for RBD includes medication and changing the sleep environment to increase safety for the person with the condition and their sleeping partner.

There are several ways to enhance both REM and non-REM sleep to reap the benefits of high quality sleep. The following tips may help improve REM sleep.

Get enough sleep

A healthy adult requires at least 7 hours of sleep per 24-hour period. Sleeping less than this reduces the number of REM sleep phases the person experiences.

Address medical conditions

Certain medical conditions, such as sleep apnea, can affect sleep quality and impact REM sleep. Addressing these conditions may help improve the overall quality of sleep.

Avoid alcohol before bedtime

As moderate-to-high levels of alcohol intake before bed can reduce the number of REM sleep phases and delay entering the first REM phase, it is advisable to avoid alcohol consumption in the hours immediately before bed.

Get 21 tips to fall asleep quickly here.

Following the same bedtime routine each day prepares the body and mind for sleep. Having a regular bedtime routine may help maximize the amount of time asleep, potentially increasing the number of REM sleep phases a person experiences.

Some good sleep habits include:

  • going to bed and waking up at consistent times
  • removing electronic devices from the bedroom
  • increasing physical activity in the day
  • keeping the bedroom cool, dark, and quiet
  • avoiding large meals and caffeine before bed

REM sleep is the stage in which most people vividly dream. These periods of sleep typically start around 90 minutes after someone falls asleep and cycle every subsequent 90 minutes.

REM sleep is important to the consolidation of information and the development of memories. Research has linked disruptions in REM sleep with an increased chance of obesity and risk of migraine.

Developing good sleep habits and having a consistent pre-sleep routine can help people improve the quality of their REM sleep and the quality of their overall rest time.