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What is REM sleep and why is it important?

July 31, 2023 - 14 min read
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    Have you ever wondered what happens during sleep that keeps us feeling refreshed and recharged for the day ahead? One of the most captivating phases of sleep is REM sleep, short for Rapid Eye Movement. It's a remarkable stage in our sleep cycle, characterized by vivid dreams and rapid eye movements under closed eyelids.

    Let’s look at what REM sleep is, its characteristics, how it differs from other stages of sleep, and the significance it holds for memory consolidation, emotional processing, and overall sleep quality.

    What is REM sleep?

    REM sleep is one of the distinct stages of sleep that occur in a repeating cycle throughout the night. It is characterized by rapid and random eye movements under closed eyelids, as well as increased brain activity resembling that of wakefulness. REM sleep is one of the four main stages of sleep, along with NREM (Non-Rapid Eye Movement) stages N1, N2, and N3.

    During REM sleep, our brains are highly active, and this is the stage where most of our dreaming occurs. Our muscles become temporarily paralyzed, preventing us from acting out our dreams physically—a phenomenon known as REM atonia. This paralysis is thought to be a protective mechanism to prevent injuries during sleep.

    Key features of REM sleep include:

    • Rapid eye movements: As the name suggests, our eyes move rapidly under our closed eyelids during REM sleep. These movements are often associated with the vivid and intense dreams that occur during this stage.
    • Increased brain activity: Despite being asleep, the brain exhibits activity levels similar to, or even higher than, those during wakefulness. This heightened brain activity is believed to play a role in memory consolidation and emotional processing.
    • Muscle atonia: REM sleep is characterized by muscle relaxation, except for the diaphragm and eye muscles. This muscle atonia prevents us from physically acting out our dreams, safeguarding us from potential harm during sleep.
    • Irregular breathing and heart rate: Breathing and heart rate may become irregular during REM sleep, though this is not usually a cause for concern.

    REM sleep is a crucial part of the sleep cycle, and its disruption can have significant effects on cognitive function, mood, and overall well-being. Healthy sleep patterns that include sufficient REM sleep are essential for maintaining optimal physical and mental health. On average, adults spend about 20-25% of their total sleep time in REM sleep, with the majority of REM sleep occurring in the later part of the night.

    What happens in your brain during REM sleep?

    While you’re in this sleep stage, an area at the base of the brain called the pons sends signals that shut off neurons in the spinal cord, temporarily immobilizing your muscles and limbs. This prevents you from acting out your dreams—for instance, running headlong into a wall if you’re dreaming you’re being chased.

    And though there’s no consensus among sleep experts as to why we dream and what our dreams mean, there is agreement that REM sleep has a huge role in our learning and memory processes and our emotional regulation.

    Why is REM sleep important?

    In short: REM sleep is crucial because it keeps your brain sharp. It is considered the mentally restorative sleep stage. 

    During REM sleep, the areas of the brain that are essential for learning and making or retaining memories (memory consolidation) are stimulated. This is when your brain consolidates, processes, and stores new information.

    Psychologist Rubin Naiman, a sleep and dream specialist at the University of Arizona Center for Integrative Medicine and the author of a paper about REM sleep deprivation (Annals of the New York Academy of Sciences), described the brain during REM sleep as a kind of “second gut” that digests all the information gathered that day. “Everything we see, every conversation we have, is chewed on, swallowed, and filtered through while we dream” and either assimilated or discarded, he said.

    REM sleep also sharpens your concentration and focus, which helps you optimize your performance at work, while playing sports, or working out— in every aspect of your life. Research suggests that when people are deprived of REM sleep they have trouble recollecting things they’re taught before falling asleep.

    Here’s how James B. Maas, Ph.D., a leading authority on sleep and performance, put it: “During REM sleep, the brain busily replenishes neurotransmitters that organize neural networks essential for remembering, learning, performance, and problem-solving,” he explained. “Conversely, depriving the brain of sleep "makes you clumsy, stupid and unhealthy."

    group of women laughing

    REM sleep and emotional health

    Besides supporting memory and mental focus, REM sleep has a major impact on mood and emotion processing. That’s because your amygdala, the same part of your brain that helps you make decisions and form memories, also processes emotions. And it activates during REM sleep.

    You’ve probably experienced how even a single night of poor sleep will leave you feeling irritable, moody, and more emotionally reactive. Several studies, confirming what you already know, suggest that REM sleep can affect how accurately you read emotions and process external stimuli.

    Matthew Walker, Ph.D., professor of neuroscience and psychology and director of the Center for Human Sleep Science at UC Berkeley, is the author of the groundbreaking book Why We Sleep. Walker and his colleagues have found that people who view emotional images before getting a good night’s sleep react less intensely to the same images the next day, compared to those who didn’t sleep well. “I think of dreaming as overnight therapy,” Walker said. “It provides a nocturnal soothing balm that takes the short edges off of our emotional experiences so we feel better the next day.”

    “We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress," he said. "By reprocessing previous emotional experiences in this neuro-chemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength. We feel better about them. We feel we can cope.”

    A meta-analysis of experimental sleep deprivation studies confirms this, finding that sleep loss had an even greater effect on emotions than on cognitive or motor function.

    In REM sleep, your brainwaves are similar to when you're awake.

    When does our REM sleep occur?

    The REM sleep stage usually starts about 90 minutes after falling asleep.

    REM sleep stages tend to be shorter during the first two-thirds of the night when the body prioritizes deeper, slow-wave sleep. With each new sleep cycle, you’ll spend more time in REM, with most of your REM sleep happening during the second half of the night.

    Because longer periods of REM sleep occur during the final hours of sleep — in the early morning, for most people — it can get cut off when you don’t spend a full seven or eight hours in bed. Meaning it’s the first to go when you set a morning alarm.

    How much REM sleep do we need?

    Most adults spend approximately 20 to 25% of their sleep time in the REM stage. But this is a ballpark figure, not set in stone, and can change over time and for many reasons. For instance, the percentage of REM sleep you get typically declines with age.

    Your sleep patterns and sleep duration change not only throughout your life, but even from day to day. How much time you spend in a particular sleep stage, including REM, can vary based on what your body needs on any given night.

    What happens when we don’t get enough REM sleep?

    Getting enough REM sleep is important for overall health and well-being. If you aren’t getting enough, you could be suffering from an undiagnosed sleep disorder such as sleep apnea or shift work sleep disorder.

    Here are some consequences of not getting enough REM sleep:

    • Increased risk of cardiovascular disease: A study found that spending less time in REM sleep is linked to a greater overall risk of death from any cause as well as from cardiovascular disease and other diseases except for cancer.
    • 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.
    • Migraines: Fragmented sleep may increase the frequency and severity of migraines.
    • Emotional reactivity: A study found that selective REM sleep deprivation in humans is associated with enhanced emotional reactivity, both at behavioral and neural levels.
    • Poor cognitive outcomes: Short REM duration may lead to memory deficit and poor cognitive outcomes.
    • Reduced ability to consolidate information and develop memories: REM sleep is important to consolidating information and developing memories.
    woman in dim room with hands over her face tired

    How to improve REM sleep

    The best way to get more REM sleep is to get more high-quality sleep. Aim to hit that sweet spot which for most people is seven to nine hours, but keep in mind that the best sleep is continuous and non-fragmented. This means that seven and a half hours of solid sleep is better than nine hours with awakenings for most people.

    Whatever you can do to improve your sleep hygiene will also boost your time in REM. There are, however, a couple of things you can do to optimize your REM sleep:

    • Maintaining a consistent sleep schedule means going to bed at the same time each night and waking at the same time each morning. This will maximize the quality of your sleep, including REM sleep.
    • Research shows that even moderate alcohol intake in the evening can disrupt your sleep cycle, and interfere with REM sleep. If your body is still processing the alcohol when you go to bed, it has a hard time getting past light sleep and into the deeper sleep stages. A few drinks close to bedtime can delay entering the first REM phase and reduce the number of REM sleep phases overall.
    • Certain medications, medical conditions, and lifestyle confines can affect sleep quality and impact REM sleep. Addressing these conditions or adjusting your sleep schedule may help improve the overall quality of your sleep.
    • Staying hydrated throughout the day and stopping drinking water about two hours before bed can help improve sleep. This ensures you aren’t losing sleep to dehydration without needing to wake up and use the restroom in the middle of the night.
    • Listening to your body by understanding your chrononotype, for example, can help you determine what you need to do for better sleep. Pay attention to when you get tired and how well you sleep after a day of certain activities or foods. Try wearing a sleep tracker to get a more granular view of your sleep cycles.

    Making the most of your sleep

    It’s clear that REM sleep is important to overall health. From short-term alterations in the ability to concentrate to long-term effects on our health, building a consistent and rejuvenating sleep schedule is critical. Now that you have some ideas for how to get more REM sleep, you can put them into practice and start sleeping (and feeling) better.

    Enhance your health and wellness

    Create a plan for a healthier life with personalized guidance from our wellness coaches.

    Published July 31, 2023

    Janet Ungless

    Janet Ungless is a health and wellness writer specializing in sleep, meditation, and mindfulness. Her work has been featured on Sleep.com, Crescent Health, Oura, Headspace, and Casper. Janet holds a Bachelor of Arts in English from the University of Pennsylvania.

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