Why do we need rem sleep

REM & NREM, Sleep Stages, Good Sleep Habits & More

What is sleep?

You may think nothing is happening when you sleep. But parts of your brain are quite active during sleep. And enough sleep (or lack of it) affects your physical and mental health. When you sleep, your body has a chance to rest and restore energy. A good night’s sleep can help you cope with stress, solve problems or recover from illness. Not getting enough sleep can lead to many health concerns, affecting how you think and feel.

During the night, you cycle through two types of sleep: non-rapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep. Your brain and body act differently during these different phases.

What happens in the brain during sleep?

Researchers continue to study sleep and its effect on us. While we’ve learned a lot about sleep, there’s still much that’s unknown.

We know that brain chemicals are very involved in our sleep cycle. Neurotransmitters are chemicals that help the nerves communicate. They control whether we’re awake or asleep, depending on which neurons (nerve cells) they’re acting on:

  • Neurons in the brainstem (where the brain and spinal cord meet) produce neurotransmitters called serotonin and norepinephrine. These chemicals keep our brain active when we’re awake.
  • Neurons located at the base of the brain are responsible for us falling asleep. It seems these neurons turn off the signals that keep us awake.

Why do we need sleep?

Sleep helps us in many ways. We need it for:

  • Growth: In children and young adults, deep sleep (sleep that’s harder to wake from) supports growth. The body releases growth hormone during this type of sleep. The body also increases production of proteins, which we need for cell growth and to repair damage.
  • Nervous system function: A lack of sleep affects our memory, performance and ability to think clearly. If a person is severely sleep deprived, they may even experience neurological problems such as mood swings and hallucinations. Sleep also helps our nerve cells. They can repair themselves, so they function at their best. And certain nerve connections get a chance to turn on, strengthening our brain and thinking ability.
  • Survival: Researchers don’t fully understand why sleep is so essential. But studies in animals have shown that getting deprived of REM sleep can shorten lifespans. Lack of sleep may harm the immune system, which protects us from infections.
  • Well-being: People who don’t get enough sleep are at higher risk for developing various health conditions including obesity, diabetes and heart problems.

What are the stages of sleep?

When you sleep, your brain goes through natural cycles of activity. There are four total stages of sleep, divided into two phases:

  • Non-REM sleep happens first and includes three stages. The last two stage of non-REM sleep is when you sleep deeply. It’s hard to wake up from this stage of sleep.
  • REM sleep happens about an hour to an hour and a half after falling asleep. REM sleep is when you tend to have vivid dreams.

As you sleep, your body cycles through non-REM and REM sleep. You usually start the sleep cycle with stage 1 of non-REM sleep. You pass through the other stages of non-REM sleep, followed by a short period of REM sleep. Then the cycle begins again at stage 1.

A full sleep cycle takes about 90 to 110 minutes. Your first REM period is short. As the night goes on, you’ll have longer REM sleep and less deep sleep.

What is non-REM sleep?

Three stages make up non-REM sleep.

Stage 1:

This stage of light sleeping lasts for five to 10 minutes.

  • Everything starts to slow down, including your eye movement and muscle activity.
  • Your eyes stay closed. If you get woken from stage 1 sleep, you may feel as if you haven’t slept at all. You may remember pieces of images.
  • Sometimes, you may feel like you’re starting to fall and then experience a sudden muscle contraction. Healthcare providers call this motion hypnic myoclonic or hypnic jerk. Hypnic jerks are common and not anything to be concerned about as this occurrence is unlikely to cause any complications or side effects.

Stage 2:

  • This period of light sleep features periods of muscle tone (muscles partially contracting) mixed with periods of muscle relaxation.
  • Your eye movement stops, heart rate slows and body temperature decreases.
  • Brain waves become slower. Occasionally, you’ll have a burst of rapid waves called sleep spindles.
  • Your body prepares to enter deep sleep.

Stages 3

  • This stage is deep sleep.
  • During this stage, your brain produces delta waves, very slow brain waves.
  • It’s hard for someone to wake you up during this stage.
  • You have no eye movement or muscle activity.
  • If you’re woken up, you may feel groggy and disoriented for a few minutes.

What happens during non-REM sleep?

During non-REM stages, your body:

  • Builds bone and muscle.
  • Repairs and regenerates tissues.
  • Strengthens the immune system.

As you age, you get less non-REM sleep. Older adults get less deep sleep than younger people.

What is REM sleep?

When you enter REM sleep, brain activity increases again, meaning sleep is not as deep. The activity levels are like when you’re awake. That’s why REM sleep is the stage where you’ll have intense dreams.

At the same time, major muscles that you normally control (such as arms and legs) can’t move. In effect, they become temporarily paralyzed.

Usually, REM sleep arrives about an hour and a half after you go to sleep. The first REM period lasts about 10 minutes. Each REM stage that follows gets longer and longer.

The amount of REM sleep you experience changes as you age. The percentage of REM sleep:

  • Is highest during infancy and early childhood.
  • Declines during adolescence and young adulthood.
  • Declines even more as you get older.

What else happens to the body in REM sleep?

Besides increased brain activity and muscle relaxation, your body goes through a series of changes during REM sleep. These changes include:

  • Faster breathing.
  • Increased heart rate and blood pressure.
  • Penile erections.
  • Rapid eye movement.

What affects sleep quality?

Chemical signals in the brain influence our sleep and wake cycles. Anything that shifts the balance of these neurotransmitters can make us feel drowsier or more awake. For example:

  • Alcohol may help people fall into a light sleep. But it reduces the deeper stages of sleep and REM sleep and leads to more disrupted sleep.
  • Caffeine and pseudoephedrine (drug ingredient) can stimulate the brain. They may cause insomnia, an inability to sleep. Watch out for caffeinated drinks such as coffee and drugs such as diet pills and decongestants.
  • Medications such as antidepressants can cause less REM sleep.
  • People who smoke heavily often sleep lightly and have less REM sleep. They may wake up after a few hours because they experience nicotine withdrawal.
  • Very hot or cold temperatures can disrupt REM sleep. We’re less able to regulate body temperature during REM sleep.

How much sleep do I need?

Many factors affect how much sleep you need. Age is a big factor:

  • Infants need about 16 hours a day.
  • Toddlers and preschoolers need about 12 hours.
  • Teenagers need about nine hours.
  • Adults need seven to eight (though some are fine with five and others need closer to 10).
  • Pregnant people often need more sleep during the first trimester.

What is a sleep debt?

If you haven’t slept well or long enough for a few days, you might create a sleep debt. Once your debt builds up, you may feel physically and mentally exhausted. Try to make sure you get enough sleep every night to avoid creating this debt. You can’t necessarily make up your debt by sleeping a lot on the weekends. It’s best to get enough sleep all week long.

Can we adapt to needing less sleep?

Generally, people don’t adapt to getting less sleep than they need. You may feel like you’re used to reduced sleep, but it still affects your function. For example, it can harm your judgment and reaction time.

What is sleep deprivation?

When you’re sleep deprived, you’re not getting the total amount of sleep you need. Signs of sleep deprivation include:

  • Falling asleep within a few minutes of lying down.
  • Feeling drowsy during the day.
  • Nodding off for microsleeps — short periods of sleep during the day when you’re otherwise awake.
  • Sleep deprivation can be dangerous. Driving while tired causes about 100,000 car accidents each year, according to the National Highway Traffic Safety Administration. It also causes 1,500 deaths. If you feel tired on the road, pull over. It’s not safe to drive if you’re drowsy.

What are sleep disorders?

According to the American Sleep Association, at least 40 million Americans experience sleep disorders each year. Another 20 million have occasional sleep issues. These disorders cause sleep deprivation, leading to problems with work, school, driving and social activities.

There are more than 70 sleep disorders. A few, known as disruptive sleep disorders, lead to moving around or making sounds. Other sleep disorders involve food. And some sleep disorders overlap with psychiatric conditions. If you have problems with sleep or feel very tired, talk to your healthcare provider about a possible sleep disorder.

Some of the most common sleep disorders include:

  • Insomnia disorder: Many people experience insomnia at some point in their lives, with trouble falling or staying asleep. Sleeping pills can help in the short-term but behavioral strategies to improve sleep including cognitive behavioral therapy for Insomnia (CBT-i) is a much better long term solution.
  • Narcolepsy: You may suddenly fall asleep during the day, even if you had a good sleep the night before. These “sleep attacks” can last a few seconds or up to 30 minutes. Talk to your provider about your symptoms and additional testing will need to be completed to diagnosis this sleep disorder.
  • Restless legs syndrome (RLS): You may feel unpleasant sensations in your legs (such as prickling or tingling). You may also have an urge to move your legs to get relief. If you have RLS, talk to your healthcare provider about medication to help improve symptoms.
  • Sleep apnea: You may experience periods of interrupted breathing while you sleep, a condition called sleep apnea. Often, getting polysomnography (sleep study) in a sleep center is the best way to get properly diagnosed and treated. Sometimes, weight loss or not sleeping on your back can help. But you may need a special device to help you breathe while you sleep.
  • Snoring: People who regularly snore can have disturbed sleep. They can also disturb the sleep of their bed partner. Snoring often leads to feeling tired during the day. Several treatment options are available for snoring.

What are good sleep habits?

Good sleep habits, also called good sleep hygiene, are practices to help you get enough quality sleep.


  • Have a sleep schedule: Go to sleep and wake up around the same time every day, even on weekends and vacations.
  • Clear your mind before bed: Make a to-do list early in the evening, so you won’t stay awake in bed and worry about the next day.
  • Create a good sleep environment: Make sure your bed and pillows are comfortable. Turn down the lights and avoid loud sounds. Keep the room at a comfortable temperature.
  • Exercise every day: Stay active but try to avoid exercising during the few hours right before bed.
  • Relax: Before bed, take a warm bath, read or do another relaxing activity.
  • See your healthcare provider: If you’ve been having trouble sleeping or feel extra drowsy during the day, talk to your provider. There are many treatments available for sleep disorders.


  • Consume caffeine, nicotine and alcohol late in the day: These substances can interfere with your ability to fall and stay asleep.
  • Lie in bed awake: It’s better to do a soothing activity, like reading, until you feel tired.
  • Nap during the day: A short nap (less than 30 minutes) is OK if you’re very sleepy. But try to avoid naps after 3 p.m.
  • Think negative thoughts: Try to avoid a negative mindset when going to bed, such as, “If I don’t get enough sleep now, I won’t get through my day tomorrow!”
  • Use electronics right before bed: Electronics, such as your phone or tablet, can interfere with your body’s production of melatonin. This hormone gets released before bed to help you feel tired.

A note from Cleveland Clinic

Far from being a state of doing nothing, sleep is an essential part of our lives. It helps our body rest, recharge and repair. There are four sleep stages — three in the non-REM phase plus REM sleep. Many factors can affect sleep quality, including the food and drink you consume before bed and room temperature. Many people experience trouble sleeping now and then. But if you think you may have a sleep disorder, talk to your healthcare provider. Common sleep disorders include insomnia (trouble falling asleep) and sleep apnea (breathing trouble during sleep). Your provider can help you get the diagnosis and treatment you need.

What is REM Sleep? - National Sleep Foundation

/ Basics of Sleep

You may have heard the term, but do you know what it means? Understanding the importance of REM helps explain why a solid night’s sleep is so important.


Most people climb into bed at night without ever thinking about the different stages of sleep that their brain and body cycle through or how these stages can affect their health. But understanding the role of REM sleep is important. This particular stage of sleep has a major impact on your memory, mental focus, and mood.


In this article you’ll learn about what REM is, why the REM portion of your sleep is so important, and how to make sure you’re achieving the right amount every night. 


Know Your Sleep Stages

Ever wonder why you are tired despite getting a full night’s sleep? Maybe you didn’t spend enough time in the deep sleep stage of your sleep. Sleep is generally divided into two stages: REM (rapid eye movement) and NREM (non-rapid eye movement). NREM is further split into three parts: starting to fall asleep, light sleep, and deep sleep. During deep sleep, your breathing slows down, your blood pressure drops, and your energy is renewed.  


During a typical night, your sleep alternates through cycles of REM and NREM sleep about every 90 minutes. The REM stage accounts for approximately 25 percent of sleep time, while the NREM stage takes up the other 75 percent. Ideally, you want to achieve five or six full sleep cycles, the equivalent to seven and a half to nine hours of sleep each night. You may feel more refreshed and rested if you wake up at the end of a cycle, instead of in the middle of one.


Understanding REM Sleep

While you’re in the REM stage of sleep, your eyes move rapidly (giving this stage its name), darting back and forth under your closed lids. It is during this state that most of your dreaming takes place. At the same time, your muscles become temporarily paralyzed—important so that you don’t attempt to act out those dreams. REM sleep involves more brain activity than NREM and is considered a more “wakeful” state, as your heart rate and blood pressure increase to levels close to what you experience when you are awake.  


Why Is REM Sleep Important?

REM sleep plays a significant role in helping your brain consolidate and process new information. This information is then retained in your long-term memory. REM sleep also helps to ensure better mental concentration and mood regulation, two things that are critical to both your daily work performance and overall quality of life. 


The negative effects from lack of REM sleep are serious: Without this critical sleep stage, your immune system could be weakened, you may experience pain more deeply, and the growth of new healthy cells and tissue in the body might be blocked. Poor REM sleep may be due to sleep disorders such as insomnia or obstructive sleep apnea, which causes you to wake during the night.


Improving Your REM Sleep 

There are apps and tools on the market that are helpful in quantifying how long you sleep and how much you toss and turn during the night. By measuring things like changes in heart rate, they may be able to estimate your REM sleep as well. But it’s also true that by simply focusing on getting a solid night of sleep, you will likely improve your chances of getting a sufficient amount of the all-important REM stage, too.


How to make sure you get the sleep you need? Wind down gradually in the evening, without TV or computers to distract you with their sleep-inhibiting blue light. Head to bed at the same time each evening to increase your odds of developing a healthy sleep schedule. And limit caffeine and alcohol before bed to improve your overall sleep.


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Scientists have not come to a consensus why we need sleep, but they do not doubt that it is very necessary

On March 14 humanity celebrates the International Day of Sleep. Instead of getting enough sleep that day, the science department of Gazeta.Ru understands what scientists currently know about the nature of sleep and its role for the body. And also in how much sleep you need and what is the danger of lack of sleep.

There is no life without sleep

We absolutely need sleep. A person can survive for quite a long time without food, a week without water, and five or six days without sleep can lead not only to serious consequences for the body, but also to death. It is no coincidence that sleep deprivation torture, which was also practiced in the dungeons of the Lubyanka to break a person, is one of the most severe. nine0197

Not only we need sleep, animals and birds also sleep. Other animals - reptiles and even invertebrates - have a resting stage. However, according to Vladimir Kovalzon, Doctor of Biological Sciences, Leading Researcher of the Institute of Ecology and Evolution Problems of the Russian Academy of Sciences , Head of the Russian Society of Somnologists , only warm-blooded animals — mammals and birds — have true sleep. And this dream is complexly organized, consists of several stages.

Sleep washes rubbish out of the head

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The need for sleep for life, as Vladimir Kovalzon told the Gazeta.Ru correspondent, was proved at the end of the 19th century by the Russian researcher Maria Manaseina . In her experiments, she kept the puppies awake, constantly stroked them, and after four or five days the puppies died.

If the body needs sleep so much, then why? The answer to this question - our body gets tired during the day and rests in a dream - ceased to be obvious when scientists found that our internal organs work in a dream and, most importantly, the brain works very actively. nine0197

How sleep works

The French researcher Michel Jouvet, who is also known as the author of the novel The Dream Thief , did the most to study the electrical activity of the brain during sleep. He found that sleep consists of two successive phases.

Phase slow wave sleep is characterized by waves of high frequency and low amplitude on the electroencephalogram (EEG). The phase of REM or paradoxical sleep is similar to wakefulness according to the EEG pattern - it is a low-amplitude high-frequency activity. nine0197

Later, scientists divided non-REM sleep into several stages, differing in depth. The transition to REM sleep occurs against the backdrop of the fourth, deepest stage. Its onset is marked by the movement of the eyeballs under the eyelids, which is why it is also called the stage of rapid eye movements (REM sleep). The cycle from light to REM sleep takes about an hour and a half for a person, and we go through four to six such cycles per night.

REM sleep is especially abundant in infants - half of the total sleep time. With age, it becomes less, and in an adult it takes about 20% of night sleep. nine0197

The function of REM sleep is still a mystery.

As Vladimir Kovalzon says, "a lot of hypotheses have been put forward on this topic, but they either cannot be verified experimentally, or they do not withstand such verification."



Only dolphins are deprived of REM sleep, at least until now scientists have not found it in them. The second feature of dolphins is unihemispheric sleep, which was discovered by Russian biologist Lev Mukhametov. Since these animals are in the water all the time, and cannot breathe underwater, they sleep with only one hemisphere of the brain, in turn, while the other hemisphere controls the movement at this time. nine0197

Hypotheses about the role of sleep

The idea of ​​learning in sleep, which appeared several decades ago, has not been confirmed. But the fact that sleep helps to learn what has been learned is a fact.

Everyone knows from their own experience that it is necessary to get enough sleep before the exam. And at first, a key role in this process was assigned to fast sleep, during which the brain allegedly processes information and long-term memory is formed. Many experiments have been carried out on animals, which, according to a special technique, were deprived of REM sleep. But the results were mixed. Then the scientists turned their attention to non-REM sleep, assigning it a key role in the mechanisms of memory. Again, no convincing results were obtained. nine0197

“This hypothesis has not been rejected, but skepticism remains,” Vladimir Kovalzon explained to a Gazeta.Ru correspondent. “In most cases, there is a connection, but it is rather weak.”

According to Vladimir Dorokhov, Head of the Laboratory of Sleep Neurobiology, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences,

if sleep is involved in memory processes, it does not play a major role.

Scientists conducted experiments in which rats were deprived of sleep by rolling them on a carousel. It turned out that sleep deprivation impaired the rats' ability to learn, but not by much. The neurophysiologist believes that, most likely, in a dream, the brain gets rid of unnecessary information, cutting off everything superfluous and leaving what is really important. nine0197

Another hypothesis is that important metabolic steps take place during sleep.

Data have been obtained that during non-REM sleep in mice, genes encoding proteins involved in the synthesis of various enzymes and other vital proteins work in the cerebral cortex and hypothalamus.

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Thus, the brain in sleep prepares for wakefulness. Perhaps at this time there are biochemical reactions that require a lot of time.

And according to the hypothesis of Ivan Pigarev, Doctor of Biological Sciences, Leading Researcher of the Institute for Information Transmission Problems of the Russian Academy of Sciences , during sleep, brain neurons switch to a different mode of operation. They cease to perceive information from the external environment and switch to information from internal organs. The activity of neurons during sleep ensures the coordination of all body systems: cardiovascular, respiratory, digestive. nine0197

Back in Soviet times, neurophysiologists Vadim Rotenberg and Viktor Arshavsky put forward a hypothesis that

REM sleep provides a mechanism of psychological protection against stress.

REM sleep usually increases with stress. According to the hypothesis of scientists, at this time the brain is trying to find a solution to a situation that a person is not able to resolve in reality. This "search activity" saves the body from the severe effects of stress.

Another important role of sleep has been recently confirmed. Answering Gazeta.Ru about the most interesting discoveries of recent times, Vladimir Kovalzon said: “Perhaps the most interesting thing is the sensational article that0203 was published on October 18, 2013 in Science ("Gazeta.Ru" wrote about this study ). A group of researchers led by the Dane Maiken Niedergaard, who is now working in the United States at the University of Rochester, discovered a previously unknown drainage system in the brain. It serves to remove large molecules that cannot leave it in the usual way. In the body, they are removed by lymph, but there is no lymph in the brain, and it was not known how this happens. The authors called this system glymphatic, from the word "glia". Astrocyte cells have channels that conduct water, and so far it has not been entirely clear why they are needed. These tubules open, water enters the intercellular fluid and flushes out all harmful substances. These tubules open during sleep and close when awake. nine0197

This is also very important for the mechanisms of development of neurodegenerative diseases such as Alzheimer's, Parkinson's, when pathological proteins are formed. Drainage removes these proteins, and this happens during sleep. And if the circulation is disturbed, they accumulate and form plaques.

Intuitively it has long been clear that sleep cleanses the brain, it is not by chance that we wake up with a fresh head. But now it has been proven using the most modern technique, two-photon microscopy.

Son bills

“The normal duration of sleep for an adult is considered to be seven to eight hours,” a somnologist, associate professor of the Moscow Medical Academy named after M.V. Sechenov Mikhail Poluektov. - The most obvious consequences of lack of sleep are a decrease in attention, memory, and performance. Labor productivity is reduced by about half, the number of errors increases.

It is estimated that the risk of getting into an accident in a sleepy person increases five times.

nine0196 Night life hits the liver

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The danger of man-made disasters through his fault is also growing. At the same time, insufficient sleep syndrome is common today, especially for residents of large cities. It is believed that out of ten actively working people, nine do not get enough sleep on weekdays.

Lack of sleep can make you seriously ill. As Mikhail Poluektov said, “people who chronically do not get enough sleep are more likely to have hypertension, bronchial asthma, gastritis, peptic ulcer disease and, as has been shown, even one and a half times higher mortality in the long term from various diseases.” nine0197

Lack of sleep is a direct path to diabetes, as it develops cell resistance to insulin.

Night workers are more likely to gain weight. Wakefulness causes hunger, and a person goes to the kitchen with something to eat. And his biological clock is not set at this time for food, and calories turn into body fat.

Depression breaks the biological clock

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Immunity also suffers from lack of sleep. This fact was experimentally verified on volunteers who were infected with rhinovirus (the virus that causes SARS) for scientific purposes.

Learn more