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What is REM Sleep?

What is REM Sleep?

Find out what REM sleep is, how REM sleep works, and ways to get better sleep using what you’ll learn.

The REM in REM sleep stands for rapid eye movement. The REM sleep cycle can sometimes be referred to as active sleep, dream sleep, paradoxical sleep, desynchronized sleep, and rhombencefhalic sleep. Now try saying that five times fast.

Some of us may already know that REM sleep is the sleep stage when dreams occur. If that’s news to you, then you’re going to love when we break down the different sleep cycles later. REM sleep is important for more than just dreams.

There are many physical and biological functions that our bodies undergo during the REM stage of sleep. This includes everything from critical physiological processes like hormone production to psychological processes like processing memories, emotions, and stress. Below we will uncover the complexities of REM sleep. We’ve included why people need REM sleep and what happens if we don’t get enough REM sleep.

What is REM Sleep?

REM stands for rapid eye movement. The term was coined by a group of scientists doing sleep studies on infants in the 1950s. The researchers witnessed that there were specific periods  during sleep where the eyes would move quickly from side to side. These periods of rapid eye movement while sleeping were then called REM sleep.

How REM Sleep Works

REM sleep can seem complicated but it’s pretty easy to understand. First, we’re going to break down what happens to us during REM sleep, including what your brain does during REM, and what happens to your body. Then we’ll look at the differences between REM and non-REM, before going deeper into the four stages of the sleep cycle.

What Happens To Us During REM Sleep?

The first thing that happens during REM sleep is our eyes start to move back and forth real fast. The eyes don’t open, they just move underneath our eyelids. At the same time, the heart rate increases during REM, and breathing patterns change.

What Happens To Your Brain During REM Sleep?

During REM sleep, your brain lights up with activity. Your brain waves speed up and move at more active and differing frequencies. This is much different than any of the other stages of sleep where your brain waves are slow and calmer.

What Happens To Your Body During REM Sleep?

The functions of the body don’t change much during REM sleep. Your eyes do move rapidly without opening, and there is usually a temporary paralysis. This is not the same as sleep paralysis. The temporary sleep paralysis that happens during REM was thought to have evolved as a self-preservation technique.

This was because it stops us from acting out dreams, and therefore, prevents us from hurting ourselves while sleeping. However, there is now evidence that we can dream during non-REM sleep stages.

What’s The Difference Between REM Sleep and Non-REM Sleep?

REM sleep is one of the most studied stages of our sleep cycle. It’s different from all of the other sleep stages. During non-REM sleep, your eyes don’t move, your brain waves slow down, and you can move your muscles.

The 4 Main Differences Between REM Sleep and Non-REM Sleep

  • Brain waves during REM are much more active than during non-REM sleep
  • Muscles are usually paralyzed during REM and we’re able to move during non-REM sleep
  • Breathing speeds up and breathing patterns change during REM while non-REM sleep involves slower breathing
  • Heart rates increase during REM and slow down during non-REM sleep

When Does REM Sleep Happen?

Understanding when REM sleep happens starts with understanding the different stages of the sleep cycle. This is because there are four stages of sleep and you cycle through them multiple times throughout the night. Research shows your first cycle of REM sleep usually occurs around 60 to 90 minutes after falling asleep.

Since REM is only one stage of the sleep cycle, the other three stages of the sleep cycle are non-REM sleep stages. A full cycle through all 4 stages of sleep takes between 90 and 120 minutes. The amount of time you spend in REM sleep increases as you complete each 90 to 120-minute cycle. The majority of your REM sleep happens during the second half of your night.

The Four Stages of Sleep

There are four stages of sleep and each one is measured by our brainwaves using an electroencephalogram (EEG). An EEG is a test that detects electrical activity in your brain. It uses electrodes that get attached to your scalp. The activity of your brain cells communicating through electrical impulses shows up as wavy lines on an EEG recording.

When you’re awake and alert an EEG will show low-aptitude mixed frequency brain waves. In the sleepy transition between awake and asleep, your alpha waves start to peak, followed by the first stage of sleep.

Sleep Stage 1 - Light Sleep: Once you nod off, theta waves take over during the first stage of sleep. Breathing is still regular during this stage and your body is not paralyzed.

Sleep Stage 2 - Light Sleep: Bursts of waves called spindles, along with biphasic waves called K-complexes replace theta waves during the second stage of sleep. The body temperature and heart rate continue to decrease at this stage as well, helping us stay asleep long enough to complete a full sleep cycle.

Sleep Stage 3 - Deep Sleep: You transition into deep when your brain starts producing delta waves. These are the slowest brain waves you’ll produce all night. This is when it’s most difficult to wake a person up. It is during deep sleep that our bodies naturally repair themselves. It is when our bones, organs, and other muscle tissues heal. Deep sleep is also when our immune system goes to work its hardest. Getting enough deep sleep can help boost your immune system.

Sleep Stage 4 - REM Sleep: During REM sleep your brain wave activity increases back to theta waves and other more irregular patterns. On the EEG machine, it almost looks as though you’re awake, but this is when you can’t move, except for your eyes. Your heart rate increases and breathing becomes more erratic during REM.

Why is REM Sleep Important?

Sleep is important for many reasons, but REM sleep is especially important. It is during this time that many pathological, psychological, and physiological processes take place.

For Dreaming

Most dreams happen during REM sleep, but not all. The REM stage is an important part of dreaming.

For Brain Health

Because newborns spend so much time in the REM sleep stage, it is widely believed that REM plays an important role in brain health and development.

For Memory

Memory consolidation happens in the REM sleep cycle and deep sleep cycle. Getting enough REM helps your brain to learn new things and commit them to memory.

How Much REM Sleep Do You Need?

How much REM sleep you need depends on your age. Newborn babies need the most REM sleep and typically spend up to eight hours in REM every day. The need for REM sleep decreases as we get older. Most adults only need to spend one or two hours of sleep in the REM stage.

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

Now that you know how much REM sleep you need and why REM sleep is important, let’s look at what happens if you don’t get enough REM sleep. Not getting enough of the right amount of REM sleep can have multiple side effects. Since overall sleep deprivation is also linked to these symptoms, it’s hard to tell if they are caused by a lack of REM sleep specifically or just a lack of sleep in general.


Short Term Effects of Sleep Deprivation


  • Challenges concentrating when awake
  • Being excessively tired during the day
  • An increase in forgetfulness and reduced memory functions


Long Term Effects of Sleep Deprivation


  • Depression and anxiety
  • Weight gain and obesity
  • Cardiovascular disease


How To Get Better REM Sleep

Getting better REM sleep is easy with a few minor lifestyle changes. Getting a new and more comfortable mattress, bedding set, or set of pillows is a great place to start. It’s hard not to get good sleep when you have a super comfy mattress with the right amount of pillows and the perfect blankets.

5 Quick Tips for Better REM Sleep

  • Go to bed at the same time every night
  • Avoid caffeine in the afternoon and evening
  • Exercise during the day
  • Eat a healthy diet full of fruits and vegetables
  • Try breathing exercises

Check out our in-depth guide of 25 Ways to Improve Your Sleep for all the best ways to get better REM sleep.

These are the fastest ways to start taking advantage of the health benefits of REM sleep.

FAQs Answered in This Blog

What Does REM Mean in Sleep?


Is REM Sleep Good?


How Much REM Sleep Do You Need?


Is REM or Deep Sleep Better?

Next article When Do Babies Sleep Through The Night?

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