Two stages of 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.

Do:

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.

Don’t:

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.

Stages of Sleep: What Happens in a Sleep Cycle

When thinking about getting the sleep you need, it’s normal to focus on how many hours of sleep you get. While sleep duration is undoubtedly important, it’s not the only part of the equation.

It’s also critical to think about sleep quality and whether the time spent sleeping is actually restorative. Progressing smoothly multiple times through the sleep cycle, composed of four separate sleep stages, is a vital part of getting truly high-quality rest.

Each sleep stage plays a part in allowing your mind and body to wake up refreshed. Understanding the sleep cycle also helps explain how certain sleep disorders, including insomnia and obstructive sleep apnea can impact a person’s sleep and health.

What Is the Sleep Cycle?

Sleep is not uniform. Instead, over the course of the night, your total sleep is made up of several rounds of the sleep cycle, which is composed of four individual stages. In a typical night, a person goes through four to six sleep cycles. Not all sleep cycles are the same length, but on average they last about 90 minutes each.

Are All Sleep Cycles the Same?

It is normal for sleep cycles to change as you progress through your nightly sleep. The first sleep cycle is often the shortest, ranging from 70-100 minutes, while later cycles tend to fall between 90 and 120 minutes. In addition, the composition of each cycle — how much time is spent in each sleep stage — changes as the night goes along.

Sleep cycles can vary from person to person and from night to night based on a wide range of factors such as age, recent sleep patterns, and alcohol consumption.

What Are the Sleep Stages?

There are four sleep stages; one for rapid eye movement (REM) sleep and three that form non-REM (NREM) sleep. These stages are determined based on an analysis of brain activity during sleep, which shows distinct patterns that characterize each stage.

Sleep Stages	Type of Sleep	Other Names	Normal Length
Stage 1	NREM	N1	1-5 minutes
Stage 2	NREM	N2	10-60 minutes
Stage 3	NREM	N3, Slow-Wave Sleep (SWS), Delta Sleep, Deep Sleep	20-40 minutes
Stage 4	REM	REM Sleep	10-60 minutes

The breakdown of a person’s sleep into various cycles and stages is commonly referred to as sleep architecture. If someone has a sleep study, this sleep architecture can be represented visually in a hypnogram.

The classification of sleep stages was updated in 2007 by the American Academy of Sleep Medicine (AASM). Before that, most experts referred to five sleep stages, but today, the AASM definitions of the four stages represent the consensus understanding of the sleep cycle.

NREM Sleep Patterns

NREM sleep is composed of three different stages. The higher the stage of NREM sleep, the harder it is to wake a person up from their slumber.

Stage 1 / N1

Stage 1 is essentially the “dozing off” stage, and it normally lasts just one to five minutes.

During N1 sleep, the body hasn’t fully relaxed, though the body and brain activities start to slow with periods of brief movements (twitches). There are light changes in brain activity associated with falling asleep in this stage.

It’s easy to wake someone up during this sleep stage, but if a person isn’t disturbed, they can move quickly into stage 2. As the night unfolds, an uninterrupted sleeper may not spend much more time in stage 1 as they move through further sleep cycles.

Stage 2 / N2

During stage 2, the body enters a more subdued state including a drop in temperature, relaxed muscles, and slowed breathing and heart rate. At the same time, brain waves show a new pattern and eye movement stops. On the whole, brain activity slows, but there are short bursts of activity that actually help resist being woken up by external stimuli.

Stage 2 sleep can last for 10-25 minutes during the first sleep cycle, and each N2 stage can become longer during the night. Collectively, a person typically spends about half their sleep time in N2 sleep.

Stage 3 / N3

Stage 3 sleep is also known as deep sleep, and it is harder to wake someone up if they are in this phase. Muscle tone, pulse, and breathing rate decrease in N3 sleep as the body relaxes even further.

The brain activity during this period has an identifiable pattern of what are known as delta waves. For this reason, stage 3 may also be called delta sleep or slow-wave sleep (SWS).

Experts believe that this stage is critical to restorative sleep, allowing for bodily recovery and growth. It may also bolster the immune system and other key bodily processes. Even though brain activity is reduced, there is evidence that deep sleep contributes to insightful thinking, creativity, and memory.

We spend the most time in deep sleep during the first half of the night. During the early sleep cycles, N3 stages commonly last for 20-40 minutes. As you continue sleeping, these stages get shorter, and more time gets spent in REM sleep instead.

REM Sleep Patterns: What Is REM Sleep?

During REM sleep, brain activity picks up, nearing levels seen when you’re awake. At the same time, the body experiences atonia, which is a temporary paralysis of the muscles, with two exceptions: the eyes and the muscles that control breathing. Even though the eyes are closed, they can be seen moving quickly, which is how this stage gets its name.

REM sleep is believed to be essential to cognitive functions like memory, learning, and creativity. REM sleep is known for the most vivid dreams, which is explained by the significant uptick in brain activity. Dreams can occur in any sleep stage, but they are less common and intense in the NREM periods.

Under normal circumstances, you don’t enter a REM sleep stage until you’ve been asleep for about 90 minutes. As the night goes on, REM stages get longer, especially in the second half of the night. While the first REM stage may last only a few minutes, later stages can last for around an hour. In total, REM stages make up around 25% of sleep in adults.

Why Do the Sleep Stages Matter?

Sleep stages are important because they allow the brain and body to recuperate and develop. Failure to obtain enough of both deep sleep and REM sleep may explain some of the profound consequences of insufficient sleep on thinking, emotions, and physical health.

Sleepers who are frequently awoken during earlier stages, such as people with sleep apnea, may struggle to properly cycle into these deeper sleep stages. People with insomnia may not get enough total sleep to accumulate the needed time in each stage.

What Affects Sleep Stages?

While there is a typical pattern for sleep stages, there can be substantial individual variation based on a number of factors:

Age: Time in each stage changes dramatically over a person’s life. Newborns spend far more time (around 50%) in REM sleep and may enter a REM stage as soon as they fall asleep. As they get older, their sleep becomes similar to that of adults, normally reaching a comparable sleep architecture by the age of 5. On the other hand, elderly people tend to spend less time in REM sleep.
Recent sleep patterns: If a person gets irregular or insufficient sleep over a period of days or more, it can cause an abnormal sleep cycle.
Alcohol: Alcohol and some other drugs can alter sleep architecture. For example, alcohol decreases REM sleep early in the night, but as the alcohol wears off, there is a REM sleep rebound, with prolonged REM stages.
Sleep disorders: Sleep apnea, Restless Leg Syndrome (RLS), and other conditions that cause multiple awakenings may interrupt a healthy sleep cycle.

How Can You Have a Healthier Sleep Cycle?

While you don’t have full control of your sleep cycle, you can take steps to improve your chances of having a healthy progression through each sleep stage.

A key step is to focus on improving your sleep hygiene, which refers to your sleep environment (the best mattress, best pillows, or sheets, etc.) and sleep-related habits. Achieving a more consistent sleep schedule, getting natural daylight exposure, avoiding alcohol before bedtime, and eliminating noise and light disruptions can help you get uninterrupted sleep and promote proper alignment of your circadian rhythm.

If you find that you have excessive daytime sleepiness or otherwise suspect that you might have a sleep disorder like sleep apnea, it’s important to talk with a doctor who can most appropriately guide your care. Addressing underlying issues may pave the way for more complete and restorative sleep cycles.

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About Our Editorial Team

Eric Suni

Staff Writer

Eric Suni has over a decade of experience as a science writer and was previously an information specialist for the National Cancer Institute.

Dr. Nilong Vyas

Pediatrician

Dr. Vyas is a pediatrician and founder of Sleepless in NOLA. She specializes in helping parents establish healthy sleep habits for children.

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STAGES OF SLEEP. DEEP, LIGHT AND REM SLEEP

We usually think of sleep as one single experience when we go to sleep every night. But our mind and body experience different phases of sleep during the night, each with its own characteristics and benefits.

DIFFERENT STAGES OF SLEEP

Sleep stages are formed by two different types of sleep: non-REM sleep (NREM sleep) and REM sleep (REM sleep). However, before we reach these periods of sleep, there is a stage where we are simply awake. To fall asleep, we begin this stage at rest.

NREM sleep stages is when our body slows down. All activity related to our brain waves, heartbeat, breathing and muscles is reduced to a lower level than when we are awake as our body uses this time to repair and improve our various systems. It is also a type of sleep that is rarely associated with the dream state (although vivid dreams can still occur, but are less likely).

Stages of non-REM sleep include:

First stage: the lightest stage of sleep. Our entry point is where we begin the transition into deeper sleep but are still easily woken up by the noises around us.
Second stage : Deeper stage of sleep when heart rate and body temperature decrease, but loud noises can still wake us up. This stage is characterized by rapid bursts of high-frequency brain waves thought to be important for learning and memory.
Third stage : Often referred to as deep sleep or non-REM sleep. It is very difficult for us to wake up in stage 3. In this stage, the body repairs tissues, builds bones and muscles, and strengthens the immune system.

REM sleep is REM sleep when our body experiences bursts of rapid eye movements and brain activity, similar to how our body behaves when we are awake. This is a type of sleep associated with vivid dreams and a kind of sleep paralysis where our muscles lose the ability to move (so it's not the stage where people sleepwalk, for example). REM sleep is vital to our memory and emotional regulation as our brain processes and clears what we no longer need.

HOW LONG IS A SLEEP CYCLE?

All of the above stages of sleep together form a whole sleep cycle, which usually lasts from 90 to 110 minutes. So, if you sleep eight hours a night, your body will complete several sleep cycles that will repeat until you wake up.

During the night, each sleep cycle is different: the deepest sleep occurs in the first half of the night, and the REM sleep occurs in the second half. So by the time you get to the early hours of the morning, you'll basically be alternating between NREM sleep and REM sleep.

HOW LONG IS EACH STAGE OF SLEEP?

During each sleep cycle, the body experiences each stage of sleep for varying durations, depending on how long you rested. Here is how long each sleep stage lasts in adults:

NREM Stage 1 : 1 to 7 minutes in our initial sleep cycle, which is 5-10% of total sleep duration.
NREM Stage 2 : 10 to 25 minutes in the initial sleep cycle and lengthens with each successive cycle, eventually accounting for 45 to 55% of our total night of sleep.
NREM Stage 3 : 20 to 40 minutes in our initial sleep cycle and accounts for about 15-25% of our total night's sleep.
REM sleep : only 1 to 5 minutes in the initial sleep cycle, but lengthens with each successive cycle.

HOW MUCH SLEEP SHOULD I GET IN THE RAPID PHASE?

As already mentioned, REM sleep begins in short periods and then gradually becomes longer. We usually have our longest REM sleep in the morning, just before waking up. That's why you often remember your dreams more clearly if you've had a long, uninterrupted night of sleep.

Since we have several intervals during the night, each of a different duration, it is not easy to determine exactly how much REM sleep we need. However, if we don't get enough sleep throughout the night, we are more likely to miss sleep cycles with longer sleep stages. Thus, an adult needs at least seven to nine hours of sleep each night.

DEEP SLEEP OR LIGHT SLEEP?

When we talk about light and deep sleep, we mean the stages of non-REM sleep. Light sleep occurs in stages 1 and 2, and deep sleep occurs in stage 3.

As we saw above, all stages of sleep are important because they work together in a cycle to allow our body to fully rest and regenerate throughout the night. Therefore, it is very important to get a good night's sleep in order to have a good rest and benefit from the different stages.

Often, when our sleep is disturbed, we lose deep sleep. This means we miss out on the time our bodies need each night to reap the benefits of phase 3 sleep, such as improving your memory and learning functions, supporting cell growth, and boosting your immune system.

If you are interested in getting enough deep sleep every night, you should rethink your sleep patterns to create the ideal conditions for a full night's rest. Some studies have also shown that exercising 90 minutes before bed can increase the duration of deep sleep (but may decrease the duration of REM sleep).

While deep sleep is vital, light sleep also has its benefits. For example, when we wake up naturally during this part of our sleep cycle, we are more likely to feel rested and ready to start the day—a very different morning feeling than when an alarm goes off while you are in deep sleep.

SLEEP CHANGES WITH AGE

If you slept until noon as a teenager and wake up at dawn as an adult, you have probably noticed how your sleep changes throughout your life. This is how our need for sleep and experience of sleep change as we age.

Newborns and infants : Babies initially need 14 to 17 hours of sleep, usually in chunks throughout the day. By their first birthday, they typically sleep between 11 and 14 hours a night, mostly at night, with little to no daytime naps. Interestingly, newborns have a completely different sleep architecture, and it also takes their bodies three months to understand circadian rhythms.
Young children : although the need for sleep (including naps) is decreasing, children around the age of five still need about 12 hours per day. As children get older through their teens, the need for sleep decreases to about 9-11 hours each night.
Adolescents : Adolescents need about 8-10 hours of sleep each night and may experience afternoon sleepiness at various stages of puberty.
Adults : Sleep cycles remain relatively stable throughout adulthood until about age 65, with the average adult needing 7-9 hours of sleep each night.
People over 65 years of age : After this age, people have slightly less NREM sleep and spend most of their sleep cycle in stage 2. This means that older people do not sleep as soundly as they did when they were younger and often need a little less sleep (about 7-8 hours).

TRACKING SLEEP STAGES

One way to understand your sleep cycles is to track them. Nightly Recharge™ by Polar gives you a detailed analysis of your sleep every morning so you can evaluate the amount and quality of your sleep.

Nightly Recharge™ has two separate metrics: Sleep Charge and ANS Charge. Sleep Charge is the charge of sleep, it is associated with the phases of your sleep. Your sleep score shows sleep duration, sleep continuity, duration of any breaks, and details what percentage of your rest was spent in REM, deep, and light sleep. Sleep Charge then compares your sleep score to your 28-day average to show how much you recovered overnight.

ANS Charge means heart rate, heart rate variability and breathing during sleep. This indicator is needed to understand how well your autonomic nervous system relaxes during the first four hours of sleep each night. Nightly Recharge™ then uses these two metrics to evaluate your overall recovery so you can decide how active you need to be during the day.

Sleep phases: what they are, what they affect and how to get enough sleep

Doctors say

Updated September 12, 2022, 14:44

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Human sleep is cyclical and consists of phases. Each of them is responsible for certain functions - from the development of cognitive skills to general health. When the body has gone through all the phases in a dream, in the morning we feel cheerfulness and a surge of strength. Lack or disturbance of sleep, on the contrary, worsens well-being, affects memory and the ability to think clearly, and chronic sleep deprivation is fraught with serious neurological disorders. We understand what sleep hygiene is and in which phase it is better to wake up in order to feel good.

Contents

What is the sleep phase
What are the types
How to sleep: the rules
How to control

What is sleep phase

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In sleep, a person restores the balance between the neuronal centers of the brain

The sleep phase is one of the stages in the sleep cycle, characterized by a certain activity of brain neurons, changes in muscle tone and eye movements. During the night, a person sequentially goes through two phases - fast (REM) and slow (NREM), which, in turn, consists of three stages. Phases and stages follow each other, forming a cycle of up to about 110 minutes each.

The sequence of these stages in healthy people is the same, but their quality and duration vary. This is due to many factors: age, gender, bad habits, stress levels, medications and diseases, including provoking frequent awakenings - sleep apnea or restless leg syndrome (RLS).

Vladislav SinitsynPhD, neurologist "SM-Clinic" in Ivanovo

“The physiology of sleep is not fully understood. It is a dynamic process that affects almost every system in the body, from the brain to metabolism and immunity. Among the main mechanisms that determine sleep, the following are distinguished.

Circadian rhythms. This is just one of the varieties of biorhythms that, in the context of sleep, determine the mode of wakefulness and night rest. The periods of the circadian rhythm can vary significantly from person to person. Some go to bed early and get enough sleep early in the morning, others go late and cannot get up early. Correction of the biological clock is carried out in the suprachiasmatic nucleus (SCN) of the anterior lobe of the hypothalamus, which is located above the optic chiasm of the brain. For example, some people with CCN damage sleep erratically during the day because they cannot match their circadian rhythms to the light-dark cycle [1].
** Melatonin ** - sleep hormone. Its concentration gradually increases with the onset of twilight, reaching a maximum by four or five in the morning. Then its level slowly decreases, and the person wakes up. Even dim lighting at first glance can delay the synthesis of melatonin and thus disrupt sleep.
Autonomic nervous system (ANS). When the sympathetic component of the ANS predominates, the metabolism is accelerated, falling asleep is difficult, and sleep is disturbed. The parasympathetic nervous system helps the body prepare for rest. In different people with different types of higher nervous activity, the ANS works differently.

With age, sleep parameters change: its duration decreases, it becomes fragmented, and the slow phase is reduced. Thus, the sleep characteristic changes even if there are no health problems.

Daytime sleep at any age is not equivalent to nighttime sleep. Melatonin is produced only at night, during the day our body has a higher temperature, which also affects sleep. In addition, it can exacerbate health problems, as the body does not fully implement the recovery program.

What are the phases of sleep

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Phases and stages of sleep alternate in a certain sequence

First comes the slow phase, followed by a shorter period of the fast phase. Then everything is repeated, a total of four to six times a night. The slow phase consists of three stages, which are replaced in turn, and one of them, the second, is repeated twice. A typical sequence of stages and phases looks like this: N1, N2, N3, N2, REM [2].

Stages of non-REM sleep

N1 - The shortest period of falling asleep, which lasts from one to five minutes. The body is not yet completely relaxed, while the heartbeat and breathing begin to slow down. It's easy to wake someone up.
N2 - a person spends almost half of his sleep in it. It is characterized by a slowing of breathing, a decrease in body temperature and a complete cessation of eye movements. At this stage, the brain is most actively processing memories, translating them into long-term memory. This is how we remember what we have learned.
N3 - during this period, the main rest and recovery of the body occurs, including the strengthening of immunity and other functions [3]. Stage N3 is the stage of deep sleep, so waking up a person going through this phase is the most difficult.

Vladislav Sinitsin:

“If you interrupt your sleep in the slow phase, then, in addition to worsening your general well-being, your concentration will be disturbed, irritability will appear, and your working capacity will decrease. ”

REM sleep

The first time it occurs not earlier than an hour and a half after the person fell asleep. With each new cycle, its duration increases. In total, REM sleep takes up 25-30% of the time. It is in the fast phase that a person sees dreams and develops key cognitive skills, such as learning or creativity [4]. On the advice of experts, it is impossible to artificially shorten the fast phase, since the body is preparing for awakening and vigorous activity, the connection between consciousness and physiological processes in the brain is turned on.

How to get enough sleep by sleep phases: rules

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Changing the basic characteristics of sleep phases can affect thinking, mood and overall health

We cannot fully control our sleep cycles, but there are steps we can take to improve the quality of our sleep. Sleep Hygiene is a set of simple rules that will help you fall asleep and sleep better.

Lada OleksenkoExpert of the Children-Butterflies Foundation, psychiatrist, State Budgetary Healthcare Institution of the Moscow Region "LCCH"

“The following recommendations should be followed.

Melatonin, which is produced only in complete darkness, is responsible for the quality of sleep. There should not be any light sources in the bedroom - a night lamp, light from a lantern in the window, a TV turned on, etc.
The body prepares for sleep gradually, so in the evening you need to reduce physical activity and limit the use of gadgets to calm the nervous system.
It is desirable to go to bed and get up at the same time, even on weekends and holidays. This is the key to healthy sleep in accordance with biological rhythms.
Ventilate the room. The optimum temperature in the room is +18 °C.
It makes sense to abstain from alcohol and smoking before going to bed. The latter, according to doctors, is a sure way to insomnia. Caffeine also impairs falling asleep and interferes with deep sleep.
Look after the bed. Use comfortable mattress, blanket, pillows and bedding. Change them regularly, avoid synthetic materials. "

How to control sleep phases

Vladislav Sinitsyn:

“Today, there are technologies that help determine what phase of sleep a person is in, as well as identify its quality. For this, an electroencephalogram (EEG) is used, which shows the difference in brain activity. In addition, in order to sleep correctly in phases, you can use the options of various sleep calculators and specialized mobile applications. But in them, as a rule, the average rate and duration are calculated: 70% - slow sleep, 30% - fast. It is impossible to increase one phase of sleep at the expense of another. But, following the general rules, you can prolong slow sleep.

Lada Oleksenko:

“To feel alert and rested, you need to wake up in the fast phase. The reliability of various gadgets that calculate the wake-up time is no more than 80%. You can do it yourself. For example, during the week go to bed at the same time, and get up at different times. So, by your own feelings, you can understand in which of the phases you woke up.

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