REM Sleep: What It Is and Why It’s Important

What Is REM Sleep?

Rapid eye movement (REM) sleep is one of four stages of sleep. During REM sleep, many aspects of brain and body activity ramp up, at times almost to the same level as when you’re awake Trusted Source Current Biology Current Biology is a general journal that publishes original research across all areas of biology together with an extensive and varied set of editorial sections. A primary aim of the journal is to foster communication across fields of biology, both by publishing important findings of general interest from diverse fields and through highly accessible editorial articles that explicitly aim to inform non-specialists. View Source . 

REM sleep was first discovered in the 1950s, when scientists studying sleeping infants noticed distinct periods when their eyes darted quickly from side to side behind closed eyelids. These rapid eye movements earned REM sleep its name.

Over time, researchers have gathered more and more data about REM sleep, including the fact that it’s the sleep stage with the most active dreaming Trusted Source Merck Manual First published in 1899 as a small reference book for physicians and pharmacists, the Manual grew in size and scope to become one of the most widely used comprehensive medical resources for professionals and consumers. View Source . REM sleep has also been detected in many mammals and other animals, highlighting its evolutionary importance. 

In people, sleep labs with specialized equipment allow researchers to see what happens when you’re asleep that makes REM sleep different from the other stages. 

Tracking REM Sleep

According to a SleepFoundation.org survey, about half of the people who use a sleep tracker consistently review the amount of REM sleep they get each night.

While consumer sleep trackers can’t perfectly measure sleep stages, they can still help identify trends over time and encourage healthier sleep habits. If your device shows consistently low REM sleep, it may be worth evaluating your sleep routine or talking to your doctor.

What Happens During REM Sleep?

During REM sleep, your eyes move rapidly behind your closed eyelids. This is one of the only visible external signs of REM sleep, but inside the brain and body, a lot more is happening Trusted Source Eunice Kennedy Shriver National Institute of Child Health and Human Development View Source :

• Your brain activity ramps up, often leading to vivid dreams
• Most of your muscles become temporarily paralyzed
• Your pulse and breathing speed up and may become less consistent

Compared to other stages of sleep, REM sleep involves heightened activity that in many ways resembles wakefulness. That said, you remain asleep, and most of your body loses muscle tone. Although we still don’t know for sure why this happens, many researchers believe this temporary paralysis helps protect us from acting out our dreams. 

When Does REM Sleep Occur?

You experience your first period of REM sleep about 60 to 90 minutes Trusted Source StatPearls View Source after falling asleep. 

During a full night’s sleep, you cycle through different stages of sleep multiple times. There are four stages, including REM sleep Trusted Source StatPearls View Source and three stages of non-REM sleep. A full sleep cycle takes about 90 to 120 minutes to complete. 

With each new cycle, you spend increasing amounts of time in REM sleep, so most of your REM sleep takes place in the second half of the night. Activity levels in your brain and body change during each stage of sleep:

• Stage 1 (Light Sleep): In stage 1, you’re just dozing off. Your brain and body start to relax, but you can still be easily awoken.
• Stage 2 (Light Sleep): In stage 2, your body and brain slow down even more. Your heart rate, body temperature, and breathing all decrease, and your muscles relax.
• Stage 3 (Deep Sleep): During deep sleep, your brain and body slow down the most. In this restorative sleep stage, your body physically repairs itself, boosting your immune system and supporting your bones, muscles, and tissue. It can be difficult to wake you up during stage 3 sleep.
• Stage 4 (REM Sleep): Your brain activity in this stage is similar to how it is when you’re awake. You experience a loss of most muscle activity, but your eyes move quickly underneath your eyelids. 

Although the sleep stages are described numerically, you don’t always progress through them in this exact order. For example, in many sleep cycles, you transition from stage 3 sleep back to stage 2 sleep before beginning a period of REM sleep.

REM vs. Non-REM Sleep

REM sleep is one of the most fascinating stages of sleep because it’s so different from the other stages. Traits unique to REM sleep that differentiate it from non-REM sleep include:

• Brain wave activity that’s more similar to wakefulness than non-REM sleep
• Temporary paralysis of most muscles compared to relaxed but movable muscles in non-REM sleep
• Irregular breathing and heart rate instead of the steady, slower breathing and pulse during non-REM sleep
• Steady movement of the eyes compared to minimal eye movement in non-REM sleep

Why Is REM Sleep Important?

REM sleep is a core part of how sleep works, so spending enough time in the REM stage is an important part of getting a healthy night’s sleep. It also plays a role in many specific aspects of physical and mental health in both the short and long term. 

• Brain Function and Development: While you’re in REM sleep, your brain is on cleanup duty to remove cellular waste Trusted Source Translational Psychiatry View Source . That helps set you up for better brain function and thinking the next day. REM sleep also promotes brain development, which is why researchers think newborns spend most of their sleep time in REM Trusted Source Current Biology Current Biology is a general journal that publishes original research across all areas of biology together with an extensive and varied set of editorial sections. A primary aim of the journal is to foster communication across fields of biology, both by publishing important findings of general interest from diverse fields and through highly accessible editorial articles that explicitly aim to inform non-specialists. View Source . 
• Dreaming: A majority of your dreams take place during REM sleep, and dreams during REM tend to be more vivid. However, REM is not the only stage in which dreams occur — that’s actually a common sleep myth.
• Emotional Processing: Dreaming and the brain activity during REM sleep play a role in how we process emotions. Consistent REM sleep helps with emotional regulation and our response to difficult events Trusted Source Current Biology Current Biology is a general journal that publishes original research across all areas of biology together with an extensive and varied set of editorial sections. A primary aim of the journal is to foster communication across fields of biology, both by publishing important findings of general interest from diverse fields and through highly accessible editorial articles that explicitly aim to inform non-specialists. View Source , and disrupted REM sleep has been associated with a worse mood and mental health conditions like depression and post-traumatic stress disorder (PTSD) Trusted Source Annals of the New York Academy of Sciences View Source .
• Memory Consolidation: REM sleep strengthens connections between brain regions, and some studies suggest it sharpens your working memory Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . During the REM stage, your brain reviews things you’ve learned recently, deciding which items to keep in your memory and which to delete. That said, some memory consolidation also takes place in deep sleep Trusted Source Current Neurology and Neuroscience Reports View Source , which reinforces the benefits of a complete night’s sleep.
• Wakefulness Preparation: By ramping up activity in the body, REM sleep may help us get ready to wake up refreshed. This heightened activity during REM sleep is also believed to help protect the cardiovascular system from a sudden surge in activity upon waking up Trusted Source National Heart, Lung, and Blood Institute (NHLBI) The NHLBI is the nation's leader in the prevention and treatment of heart, lung, blood and sleep disorders. View Source .

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How Much REM Sleep Do You Need?

In adulthood, most people need about two hours of REM sleep each night. But infants and children need more REM sleep, because their brains are still rapidly developing. For example, newborn babies spend around eight hours in REM sleep each day. 

How much time you actually spend in REM sleep can vary from night to night. On a night when you’re short of sleep, your total REM time can get cut short. This can trigger your brain to initiate more REM sleep the following night, which is known as a REM rebound Trusted Source StatPearls View Source . Some research also suggests that REM sleep may increase Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source after learning new information.

What Happens if You Don’t Get Enough REM Sleep?

Because REM sleep enables better brain function, memory, and emotional regulation, a lack of REM sleep can cause a range of issues. On top of that, a lack of REM sleep circumvents healthy sleep overall, contributing to sleep deprivation. In the short term, signs of sleep deprivation can include Trusted Source Medline Plus MedlinePlus is an online health information resource for patients and their families and friends. View Source :

• Difficulty concentrating
• Excessive daytime sleepiness
• Forgetfulness or poor memory
• Irritability or frustration
• Greater risk of accidents

Over the long term, insufficient sleep can weaken your immune system and raise your risk of conditions like heart disease, diabetes, depression, and anxiety. 

How Can You Improve Your REM Sleep?

If you want to get more REM sleep, your first step should be to shore up the quantity and quality of your overall sleep. If you’re not getting enough sleep each night, the odds are that you’re spending less time in REM Trusted Source Sleep Medicine Reviews View Source than you need. 

To avoid this, start by adopting healthy sleep habits that reinforce your sleep hygiene. One important way to do this is to maintain a consistent sleep schedule that budgets enough time for a full seven to nine hours of total sleep. This helps reinforce your body’s internal clock, or circadian rhythm, which is essential in regulating your REM sleep.

You also want to avoid too much artificial light at night, whether from overhead lights, lamps, or screens. This isn’t just because it’s easier to fall asleep in a dark room. Too much light at night can disrupt your circadian rhythm and interfere with quality REM sleep Trusted Source International Journal of Environmental Research and Public Health View Source .

Other ways to get better REM sleep are based on eliminating factors that short-circuit normal sleep cycles. Things that can throw off REM sleep include: 

• Excess stress
• Consumption of alcohol or cannabis at night
• Taking certain medications, including some sleep aids

Many sleep disorders, including insomnia and sleep apnea, can prevent you from getting adequate REM sleep. For that reason, it’s important to talk with a doctor if you have ongoing or worsening sleep problems or symptoms of an underlying sleep disorder.

Using Sleep Data to Get More REM Sleep

Many people use sleep-tracker data to make meaningful changes to their nightly routines—and REM sleep is often a key focus. These behavioral changes can lead to deeper, more restorative sleep and longer periods of REM. The graph below highlights some of the most common adjustments people report making based on sleep-tracker insights.

What Sleep Disorders Are Associated With REM Sleep?

Not everyone has typical patterns of REM sleep. Certain sleep disorders are associated with abnormal REM sleep.

• REM Sleep Behavior Disorder (RBD): Some nights, people with REM Sleep Behavior Disorder don’t experience the expected temporary muscle paralysis when they enter REM sleep. As a result, they may act out their dreams, such as by shouting, punching, kicking, or jerking in their sleep. This can lead to injuries to themselves or their partners. RBD has been found to frequently precede neurodegenerative disease.
• Narcolepsy: Narcolepsy is a rare condition of extreme daytime sleepiness, and it may also involve temporary losses of muscle control while awake. People with narcolepsy have abnormal REM sleep patterns, including a tendency to quickly enter REM after falling asleep Trusted Source Merck Manual First published in 1899 as a small reference book for physicians and pharmacists, the Manual grew in size and scope to become one of the most widely used comprehensive medical resources for professionals and consumers. View Source .
• Nightmare Disorder: A person with nightmare disorder Trusted Source Journal of Sleep Research View Source regularly experiences intense and distressing nightmares. These bothersome nightmares arise during periods of REM sleep.
• Obstructive Sleep Apnea (OSA) and Central Sleep Apnea (CSA): Although breathing disruptions from sleep apnea do not occur exclusively during REM sleep, they do affect how much REM sleep you get. People with sleep apnea have fragmented sleep cycles, which can reduce their ability to get adequate and consistent REM sleep.
• Insomnia: Like sleep apnea, insomnia can cause fragmented and restless sleep. As a result, people with insomnia may struggle to get enough high-quality REM sleep.
• Insufficient Sleep Syndrome (ISS): ISS is when a person voluntarily cuts their sleep short, such as for work or social activities. Because they don’t get enough total sleep, people with ISS often have reduced REM sleep time.

When Should You Talk to Your Doctor?

You should talk to your doctor if you’re having any sleep problems that are severe, long-lasting, or getting worse. If you notice that poor sleep is affecting you when you’re awake, your doctor may be able to help. 

Working with a doctor can help determine if you have any underlying sleep disorder or if there is another cause of your difficulty sleeping. Based on that, they can help develop a treatment approach to improve your sleep.

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