REM Sleep: Everything You Need To Know

Of all the sleep stages we cycle through hour after hour and night after night, REM sleep is probably the most “famous.” Most people know that we do some of our best dreaming during REM sleep, but there’s a lot more going on than meets the rapid-eye movement. Dylan Petkus, M.D., says we can almost think of REM sleep as the “brain’s night shift.” In addition to being the sleep stage where our most vivid (and memorable) dreams occur, he says that memory consolidation, emotional balance, and brain development are all a part of the process. (1) (2) (3)

Note: The content on Sleepopolis is meant to be informative in nature, but it shouldn’t be taken as medical advice, and it shouldn’t take the place of medical advice and supervision from a trained professional. If you feel you may be suffering from any sleep disorder or medical condition, please see your healthcare provider immediately.

Long Story Short

• REM sleep is the fourth stage of sleep. Its hallmark is rapid eye movement, hence its name.  
• REM sleep is characterized by irregular breathing, elevated heart rate, and muscle atonia.
• REM sleep is most commonly associated with dreaming, but memory consolidation, emotional processing, and brain development also occur during this sleep stage.

What Is REM Sleep? 

REM sleep (or Rapid Eye Movement sleep) is a stage of sleep where your eyes move rapidly, and your brain activity is comparable to that of a waking state. People also experience their most vivid dreams during REM sleep, but our bodies are in a state of temporary paralysis to keep us from acting out those dreams thanks to our reticular activating system (RAS). (4) (5)

What Happens During REM Sleep?

Most people understand REM sleep to be the stage where dreaming occurs. What many people don’t know is that during REM sleep, our bodies are busy with a host of activities and functions. 

REM Sleep and Dreaming

REM sleep is also known as “dream sleep.” (3) While dreaming was once thought to be limited to the REM sleep stage, researchers have discovered that dreams can also occur in other sleep stages. Dreams outside of REM are typically not as vivid or memorable as REM dreams, and dream recall outside of REM sleep is limited. (6)

“During REM sleep, your entire body is completely paralyzed except for your eyes, which rapidly move in different directions as you sleep — hence the name REM — and thermoregulation, your body’s ability to control internal body temperature, is reduced,” says Dr. Dan Gartenberg, sleep scientist and sleep health advisor for CPAP.com  

Other physical goings-on during REM sleep include: 

• Complete loss of muscle tone (muscle atonia) (7) 
• Irregular and rapid breathing (7)
• Increased heart rate (7)
• Brain waves resembling those of a waking state (7)

Stages of Sleep: Non-REM vs. REM Sleep

Sleep occurs in two phases: nonrapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. These phases are further broken down into four stages that move from light to deep sleep: N1, N2, N3, and REM. With a full night’s sleep, your body moves through these stages in sleep cycles. Most people will go through four to six sleep cycles every night, each lasting about 90 minutes. (7)

N1 (Stage 1) 

N1 sleep is the lightest stage of sleep when you drift off to sleep. Your body retains some muscle tone, and your breathing is regular. This stage can last anywhere from one to five minutes and accounts for 5 percent of your total sleep time. (7)

N2 (Stage 2) 

This is a deeper sleep stage during which your heart rate and body temperature drop. Brain wave data reveals the presence of sleep spindles and K-complexes (or long delta waves) during N2 sleep, both of which play a key role in memory consolidation. (7) The first N2 stage of the night typically lasts somewhere around 25 minutes, and successive N2 stages lengthen as the night progresses. N2 sleep accounts for approximately 45 percent of your total sleep time. (7)

N3 (Stage 3) 

Also known as slow-wave sleep (SWS), N3 is the deepest stage of sleep. It’s also known as deep sleep or delta sleep because brain wave data reveals the presence of, you guessed it, delta waves. N3 is the sleep stage during which the body tackles bone and muscle building, releases hormones for growth and repair, and cytokines for immune strengthening. It’s the most difficult sleep stage to awaken from and, as such, the one most commonly associated with sleep inertia. With age, people spend less time in N3 sleep, picking up more time in N2. (7)

REM (Stage 4) 

The fourth and final sleep stage is REM sleep. This stage is marked by erratic and irregular breathing rates, rising heart rates, and muscle atonia (reduced muscle tone that prevents us from acting out our dreams). (7) Brainwave activity reveals the presence of beta waves, which are remarkably similar to brainwave activity in a waking state. This is the stage where most dreaming occurs and is typically less restful than other sleep stages. (7)

Sleepers typically hit their first REM sleep stage somewhere around 60 to 90 minutes into their sleep cycle. (7) Like N2, initial REM stages are short and progressively get longer as the night wears on. For this reason, most of our REM sleep occurs during the second half of the night. Initial REM stages can be as short as 10 minutes, while later REM stages can last up to one hour. (7)

Why Is REM Sleep So Important? 

According to Petkus, REM sleep is vital for solidifying memories, enhancing learning, and supporting logical reasoning and decision-making. Ultimately, a lack of REM sleep has been linked to cognitive impairments and difficulties in these areas (8). 

Memory and learning. Petkus tells us, “One of the key roles of REM sleep is memory consolidation. It’s like hitting the save button on your day’s experiences and lessons, making sure they stick.” And research corroborates as much, with studies showing that REM sleep enhances memory processing and retention, making it essential for learning new things.  (1)

Emotional balance. In terms of emotion regulation, Petkus says REM sleep is like “a natural therapy session where your brain processes emotional memories and reduces the impact of fears.” As a matter of fact, one recent study found that REM sleep has a protective quality, playing a key role in weakening the grip of fearful memories, making them less intense over time. (2)

Brain development. Research shows that REM sleep plays a role in brain development. This makes it especially important for newborns, as it does some pretty heavy lifting to support the development of their central nervous system and the formation of mature neural connections. (3)

Physical health. Insufficient REM sleep has been associated with increased oxidative stress (which can lead to cardiovascular issues like hypertension and heart disease) and disrupted immune function, leaving the body more susceptible to illnesses. (9)

Higher death rates. Research suggests that improvements to REM sleep may reduce the risk of early death. One study from 2020 found that even something as small as a 5 percent reduction in REM sleep was associated with a 13 to 17 percent increase in mortality for middle-aged men and women and older men. (10)

How Much REM Sleep Do We Need? 

According to Petkus, adults need about 1.5 to 2 hours of REM sleep each night, which roughly accounts for 20-25 percent of our total sleep time. (7) Explaining further, Petkus says we should think of our REM sleep time as an essential maintenance window for our brain — if we’re not hitting this mark, it’s like trying to run a computer that hasn’t been updated in over a year. (7)

And while adults only spend about 25 percent of their sleep time in REM, infants need far more, as their cognitive development is in high gear. As such, babies spend approximately 50 percent of their total sleep time in REM sleep. As they mature, those high requirements for REM sleep begin to drop, eventually falling more in line with adult REM requirements. (11)

Tips for Getting Enough REM Sleep

According to Gartenberg, “Prioritizing sleep at night by having a consistent sleep schedule is one of the most effective ways to get a healthy amount of REM sleep.” He adds that practicing good sleep hygiene can also help — more on that below.  

Nix the Caffeine, Sugar, and Alcohol

Sleep research consistently shows that sugar, caffeine, and alcohol can have a detrimental impact on sleep duration and quality. For this reason, Gartenberg suggests cutting these sleep stealers from your diet. If that’s not feasible, you could eliminate them in the late afternoon and evening so your REM sleep doesn’t take a hit. We’ll add here that heavy meals won’t do you any favors either. (12)(13)

Curb Blue Light Exposure

“Decreasing (or eliminating) the amount of time spent on your devices before bed can also help you get enough REM sleep,” says Gartenberg. “Blue light deters the body from releasing melatonin (aka the sleep hormone), which helps your body wind down and get ready to fall asleep.” If you’re wondering what the trade-off is between sleep and your iPhone, one study found that reducing blue light can increase REM sleep by 13.9 minutes (14).

Optimize Your Sleep Environment 

“Other simple hacks to improve REM sleep include keeping an optimal sound, light, and temperature environment at night,” says Gartenberg. Ideally, your bedroom should be dark, quiet, and cool. (13) 

Sleep Disorders Associated with REM Sleep

Sleep disorders and REM sleep share an interesting relationship. In some cases, certain sleep disorders only occur during REM sleep, and in others, sleep disorders may prevent sleepers from achieving REM sleep or enough REM sleep. Here’s a quick rundown.

Nightmare Disorder

Nightmare disorder is a parasomnia characterized by frightening and vivid dreams that may cause significant distress and impaired functioning to the sleeper. Nightmares stemming from nightmare disorder typically occur during REM sleep, and it’s relatively rare, affecting only about 2 to 8 percent of the population. (15)

Obstructive Sleep Apnea 

Obstructive sleep apnea (OSA) is a sleep disorder in which the throat muscles relax into the back of the throat and block the sleeper’s airway, causing them to stop and start breathing repeatedly. As such, frequent awakenings are a common symptom of sleep apnea. Ultimately, Gartenberg says those repeated awakenings make it much more difficult to reach REM sleep. (16)

Narcolepsy 

Characterized as both a neurological disorder and a sleep disorder, narcolepsy is a condition in which people experience sudden episodes of sleep. More specifically, those with narcolepsy usually skip over stages N1, N2, and N3 and fall directly into REM sleep — often at inopportune times. During these episodes, REM sleep can last anywhere from a few seconds to a few minutes. (7) 

REM Sleep Behavior Disorder (RSBD)

REM Sleep Behavior Disorder, or RSBD, is a rare parasomnia that affects only about 0.5 percent of adults. As its name implies, REM Sleep Behavior Disorder occurs during REM sleep. Hallmarks of the conditions include unpleasant dreams with violent content. And while most of us experience muscle atonia that prevents us from acting out our dreams, those with RSBD don’t seem to have the muscle atonia that keeps their movements in check — this can lead to violent kicking, punching, and limb movements. (7)  

Rapid Eye Movement and Dream Imagery 

As we mentioned earlier, while dreams can and do occur in other sleep stages, the REM stage of sleep is where most dreaming occurs. Whereas dreams outside of REM tend to be flashes of visual imagery with no narrative, dreams during REM sleep tend to be more hallucinatory, story-like, and vivid. Dreams across sleep stages also differ in terms of recall. Sleepers typically have higher recall rates for REM dreams, while dreams outside of REM sleep are usually unremarkable. (6) 

Pulling the covers back on dreaming during REM sleep, one recent study found that rapid eye movements (a unique characteristic of REM sleep) may be a reflection of dream content itself. Essentially, rapid eye movements may be an indicator of gaze shifts inside the dream. Researchers posit that rapid eye movements can also be a visual confirmation of the various cognitive processes that occur during REM sleep. (17)

FAQS

The Last Word From Sleepopolis 

People associate REM sleep with dreaming, but there’s a whole lot more to this sleep stage. The TLDR: REM sleep plays a crucial role in our cognitive competence and logical reasoning. To improve your REM sleep quality, consider some strategic tweaks to your sleep hygiene. 

Sources

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Gartenberg, Dan. Author Interview. August 5, 2024.

Dylan, Petkus.  Author Interview. August 6, 2024.