Deep and superficial sleep in an adult. Fast and slow sleep phases - characteristics and their effects on the human body

The alternation of activity and rest is a regular and natural process for any living organism. It is curious that for a normal life, a panda needs to sleep up to 22 hours a day, and African elephants need 180 minutes to fully rest. Much more complicated is the nature of human sleep, which is a cunning interweaving of cycles, periods and phases. Working capacity, mood, well-being directly depend on their quality and duration. Sleep scientists have proven that the most important for people is the slow phase, as well as its integral part, which is responsible for the regeneration of the body after a whole day of activity - deep sleep. The norm for an adult ranges from 90-120 minutes, taking into account the number of cycles.

What does deep sleep mean?

The daily journey to the realm of Morpheus in people is cyclical. Standard night rest is divided into two radically opposite phases, called slow and fast. The first is deep, the process of falling asleep just begins with it. Slow-wave sleep is characterized by 4 smoothly changing periods:

1. Doze, when the brain still continues to function and process the information accumulated during the day. Perhaps the appearance of the so-called. sleepy visions that have a clear connection with reality.
2. Sleep spindles or the process of falling asleep. Brain activity is minimized, consciousness is dulled. But since sleep is still superficial, due to the increased threshold of perception, a person can react sharply to stimuli from the outside and wake up.
3. Deep dream. The muscles are completely relaxed, all body processes are blunted to the maximum, only weak electrical impulses enter the brain.
4. Delta sleep. It is he who is responsible for the depth and required quality of sleeper's rest. At this time, body temperature drops, respiratory processes and blood circulation slow down. A person is not affected by any kind of irritants, it is quite difficult to wake him up. 80% of dreams fall just at this time.

After all 4 periods, it is time for REM (paradoxical) sleep. Based on the total duration of night rest, the slow and fast phases replace each other up to 4-5 times. Speaking specifically about deep sleep, it can be recorded exclusively with the help of an electroencephalogram approximately 1.5 hours after falling asleep, the duration is up to 10 minutes. While the sleeper is in the kingdom of Morpheus, the duration of further deep periods grows, reaching several tens of minutes in the morning. From cycle to cycle, the phase of REM sleep rapidly increases, while the depth, on the contrary, falls.

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The mechanism of influence on the human body as a whole

The importance of the slow phase for active life is undeniable. During the night, in the process of deep sleep, the body is updated, energy resources are replenished, cells are regenerated. Besides:

• by reducing the rate of metabolic processes, energy is accumulated;
• the immune system is activated, being at the top of activity;
• growth hormone responsible for catabolism is synthesized (proteins are formed from amino acids instead of splitting, then they strengthen the muscles as a building material and contribute to the formation of new cells);
• the depth of breaths changes their frequency, due to this, the organs are maximally saturated with oxygen, and the likelihood of developing hypoxia is excluded;
• intellectual resources are updated, and the information accumulated over the previous day is systematized and deposited in memory;
• the heart muscle recovers due to the low frequency of night contractions.

Does quality deep sleep affect intelligence?

The observed norms affect not only the dreams of an adult, but are also extremely important for his mental abilities. This was confirmed by special studies conducted with the participation of volunteers. The essence of the experiment was simple - before going to bed to rest, people were asked to remember a certain number of words, unfamiliar and unrelated to each other.

As a result, participants who had a long deep sleep phase were able to recall much more information in the morning. The conclusions are obvious - with a reduction, violation or complete absence of this important stage, normal life will be disrupted: memory will deteriorate, attention will become scattered, performance will be at zero. And if the phase of REM sleep can be easily compensated for by several tens of hours of good rest, then the normalization of the daily regimen will not help restore the strength lost due to the absence of its deep “brother”.

What should be the norm for the duration of healthy sleep

It is believed that the optimal time needed for a person to sleep at night is 7-9 hours. However, as practice shows, these values ​​are conditional. So, Napoleon was more than enough 4 hours a day to restore his intellectual and volitional abilities, while the recognized genius Einstein needed 2.5 times more time for the same purposes.

And yet, the values ​​​​of the norm of deep sleep for an adult are extremely important, which was proved by British scientists. The experiment involved 110 subjects of different ages who had never suffered from insomnia:

1. People aged 20-30 slept an average of 8 hours, and their deep sleep lasted 118 minutes.
2. The second group of participants aged 31-55 showed results in 7 hours and 85 minutes, respectively.
3. The night rest of the subjects of retirement age was 6.5 hours, deep sleep accounted for 84 minutes of this time.

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The results obtained made it possible to assert with firmness that the duration of a person's stay in one or another stage of sleep is influenced by age markers, daily routine, body weight, level of physical activity, general health and the specifics of the course of psychological processes.

Thus, a "normal" night's rest is a purely individual concept. A person should sleep exactly as much as his body needs for full recovery. If we talk about the norms, then deep sleep should account for up to 70% of the total duration of the "embrace of Morpheus."

What are the symptoms of not getting enough sleep at night?

Trouble falling asleep, feeling unwell after waking up, disruptions in nightly rest hours are three large groups of sleep disorders. They entail:

• lethargy, fatigue, poor performance throughout the day;
• reduced mental activity;
• muscle weakness;
• apathy, irritability, bad mood, in advanced cases - the development of depressive conditions;
• lack of any kind of motivation.

Single manifestations of such symptoms are not harmful to health, but the duration and systematic nature of the described conditions lead to malfunctions in the endocrine system, psychological problems.

In the case of a chronic lack of adequate sleep, somatotropic hormone stops being produced, a person's appearance undergoes a number of unpleasant changes - his stomach grows, excess weight forms. In addition, a sleeper at night has short-term stops in breathing, the so-called. apnea syndrome. It entails increased daytime sleepiness, which disrupts concentration and can lead to unfortunate consequences (for example, accidents on the road or injuries at work). Among other things, sleep apnea is a provocateur of strokes and heart attacks.

Main causes of violation

Violation of the deep sleep phase is often provoked by somatic or psycho-emotional problems.

Among them:

• chronic stress and depression;
• permanent overvoltages;
• heavy physical activity;
• heat;
• severe poisoning, other problems in the gastrointestinal tract;
• cardiovascular diseases;
• malignant neoplasms.

For any person to be healthy, it is important to have a healthy and regular sleep. Every night you need to sleep a certain number of hours in order to feel good and be productive the next day. But sleep is a complex set of biological rhythms, including at least 4-5 cycles. Each of these cycles is characterized by a short and a long phase of sleep. Moreover, it is the last phase that is very important, because it is responsible for the restoration of the body. What is the norm of deep sleep and what is this concept, we will consider below.

What is deep or non-REM sleep?

As soon as a person falls asleep, a slow phase begins, which includes deep delta sleep. After a while, it is replaced by a fast or paradoxical phase. It is characterized by the presence of sleep, but at the same time, a person may have movements and sounds.

The ratio of deep and light sleep changes throughout the night and towards the end it is more and more deep sleep that prevails.

In addition, if a person suffers from some pathologies, his deep sleep time may increase, since during this period the body recovers as much as possible. And in case of illness, recovery is needed much more, so this phase increases.

How does the quality of deep sleep affect intelligence?

Scientists have repeatedly conducted experiments, the purpose of which is to find out what is the norm of deep sleep and how this process affects the state of the body. It has been proven that during deep sleep there is a recovery of the body and an increase in mental abilities. So, the volunteers were called some words that had no connection with each other just before going to bed. It was found that the longer the phase of delta sleep lasted, the more words the subject could remember.

These studies allowed scientists to conclude that depriving a person of the deep phase of sleep is tantamount to the complete absence of this physiological process. If you shorten deep sleep, concentration of attention will begin to be lost, working capacity will drop, and memory will deteriorate.

What happens during deep sleep

I must say that each person has his own rate of deep sleep per night. Some can sleep 5 hours, and this is enough for them, while others do not have enough and 9. The older a person is, the less need he has for sleep. So, the rate of deep sleep in children (and it is up to 80% of the total sleep duration) should be 7-9 hours in total, and for adults this figure is already slightly less - 5-7 hours.

In general, the deep sleep phase is divided into the following stages:

1. At the first stage, all the events that happened during the day are recorded in deep memory. The brain analyzes the difficulties it has encountered and looks for solutions to them.
2. The next stage is the so-called "sleep spindles". At this time, the heartbeat and breathing slow down, the muscles completely relax.
3. The third stage is a deep delta sleep phase lasting 15-20 minutes.
4. Then comes the most pronounced delta sleep, during which it is difficult to wake a person. It is at this time that the body resumes its working capacity as much as possible.

If you wake up in the deep sleep stage, you will feel tired, overwhelmed, so it is important to wake up at the end of the REM phase. It is during this period that the senses are most active, so even minimal noise can wake a person up.

So, during deep sleep, the human body performs the following actions:

• all metabolic processes are slower, as the body tries to save energy;
• the brain consumes less oxygen;
• the activity of the parasympathetic system increases, which causes a decrease in blood pressure, heart rate and blood flow velocity;
• the activity of the digestive system decreases;
• the adrenal glands synthesize the main hormones with less intensity;
• growth hormone is produced;
• all body cells are restored;
• the immune system is activated to the maximum.

How long should deep sleep last?

It is impossible to say exactly what is the rate of deep sleep in a person. For example, Napoleon stated that four hours of sleep a day is enough for him, and Einstein slept all 10. But nevertheless, a certain norm of deep sleep in adults, by which one can navigate, has been established. For this, an experiment was conducted in which many patients of different ages participated. The results showed that at a young age, you need to have 7 hours of deep sleep, on average - half an hour less, and for retirees, the duration of this phase is reduced to 6 hours.

Thus, the duration of the delta phase depends on age, daily routine, psychological characteristics, weight and general health. At the same time, it is very important that everyone gets enough sleep just as much as he needs it, so that the body has time to recover. Otherwise, psychological problems will begin first, and then deviations in the work of the endocrine system will appear.

Causes of disturbed delta sleep

Occasionally, sleep disturbances can occur in everyone, but such rare manifestations do not cause serious changes in the body. So, if one night you need to not sleep for the sake of completing a project or term paper, preparing for an exam, and other goals, the body will be able to compensate for the loss of rest. To do this, you can spend more time on another day and sleep.

But if a good rest is lost or reduced for a long time, you need to look for the cause of this phenomenon. Most often, the problem with the delta phase is observed in the following situations:

• psychical deviations;
• internal diseases;
• chronic stress;
• diseases of the musculoskeletal system;
• diabetes;
• high blood pressure;
• heart disease;
• prostatitis and other male diseases.

To get rid of violations of deep or delta sleep, it is necessary to find out the cause of this phenomenon. Most often, this can be done on your own, but sometimes it is recommended to seek help from a somnologist.

For example, sleep is often disturbed by workaholics who have a very busy working day. They try to do as much as possible in a day to increase their earnings. But at the same time, such people do not take into account that chronic lack of sleep leads to a decrease in working capacity, loss of concentration and ability to memorize. Therefore, all the work still cannot be done, and the body suffers greatly from processing and lack of sleep.

Especially such a habit is in people who are engaged in mental work. Due to the absence of severe physical fatigue during work, they try to do as much as possible in a day. As a result, constant chronic fatigue leads to the following consequences:

• Periodically, infectious diseases appear, as the body is depleted, and the immune capacity cannot cope with the increased load.
• The person becomes less attentive. He makes more mistakes. In this condition, it is especially dangerous to drive a car.
• Lack of sleep increases body weight.
• Cardiac pathologies appear, the risk of developing oncological neoplasms increases.
• Appearance deteriorates significantly. Bags appear under the eyes, skin color becomes unhealthy, wrinkles may form.
• Due to the fact that the brain does not rest normally, it ceases to cope with the entire load. Memory problems begin, difficulties arise with the processing of a large amount of information.

Methods for correcting deep sleep

Despite the fact that each person has his own individual length of the deep sleep phase, its lack has serious consequences for the body. Therefore, it is important to make every effort to maximize the percentage of delta sleep at night. To do this, you can do the following:

• Make a sleep schedule, which will indicate what time you need to go to bed and wake up. If you stick to it constantly, the body will get used to it, and sleep will be better.
• Shortly before bedtime, it is recommended to visit the fresh air and perform light physical exercises.
• It is necessary to give up bad habits, especially smoking.
• Prepare a room for sleep - remove light sources, ensure complete silence.

Those who are professionally engaged in the study of sleep and its deviations also give their advice on how to make delta sleep longer.

Scientists have paid attention to sleep relatively recently, which is strange, given how much of our lives we spend in a dream. After the scientific interest in sleep processes arose, so-called sleep centers appeared at Harvard and the University of Pennsylvania, numerous studies were carried out and conclusions were drawn. In this article, you'll learn what the science of sleep is, why many people can't sleep, and some practical exercises for healthy sleep and more energy.

First steps in the science of sleep

The pioneer of chronobiology was the French scientist Michel Siffre, who studied biological rhythms in a harsh experiment on himself. He lived in an underground cave with a bed, a table, a chair, and a phone to call his research team.

Michel Siffre during the experiment

His underground home was lit with just one light bulb with a soft glow. From food - frozen foods, a few liters of water. There were no clocks, no calendars, and no way of knowing what time it was on the surface, day or night. And so he lived alone for several months.

A few days after descending into the cave, Siffre's biological clock began to work. He later recalled how he felt during the experiment:

My sleep was wonderful. My body itself chose when to sleep and when to eat. It is very important. My cycle of sleep and wake up did not last 24 hours, like people on the surface of the earth, but a little longer - about 24 hours and 30 minutes.

Thus, despite the absence of sunlight and any knowledge of whether it was day or night, his circadian rhythms continued to work.

After this experiment, many scientists became interested in the study of sleep. New research has helped to figure out how much sleep you need, why you need to do it and how you can make up for the lack of sleep.

How much sleep do you need

How much sleep do you really need? To answer this question, let's turn to the experiment of scientists from the University of Pennsylvania and the University of Washington.

The researchers collected 48 healthy men and women who were accustomed to sleeping 7-8 hours a night. The participants were then divided into four groups.

People from the first group had to go without sleep for three days, from the second - to sleep 4 hours a day. Participants from the third group were allowed to sleep for 6 hours a day, and from the fourth - for 8 hours.

The three groups, who slept 4, 6, and 8 hours a day, had to do this for two weeks. During the experiment, scientists observed the physical health and behavior of the participants.

As a result, the group of participants who slept for 8 hours a day did not experience any impairment during the entire experiment - cognitive decline, deterioration in reaction, or memory lapses. At the same time, in people who slept 6 and 4 hours a day, all indicators gradually worsened.

The 4-hour sleep group performed worse, although not by much, than the 6-hour group. In general, two significant conclusions were drawn from the experiment.

First, lack of sleep tends to accumulate. In other words, sleep deprivation has a neurobiological cost that only increases over time.

After one week of the experiment, 25% of the participants who slept 6 hours a day fell asleep intermittently at various times during the day. After two weeks, people in this group had the same performance as if they had spent two days without sleep at all.

The lack of sleep gradually accumulates.

The second conclusion is no less important: the participants did not notice a decrease in their performance. The participants themselves believed that their performance deteriorated over several days, and then remained at the same level. In fact, their performance continued to decline throughout the experiment.

We don't notice cognitive decline with lack of sleep.

It turns out that we assess our condition very poorly and cannot accurately determine how well our cognitive functions are working. Especially in today's environment of constant social activity, caffeine and many other factors that help to feel fresh and alert, even if in fact it is far from being the case.

The cost of lack of sleep

The irony is that many of us suffer from lack of sleep in an effort to earn more. But no matter how many extra hours you spend working instead of getting enough sleep, it will not increase your productivity much. Your attention, memory and other functions deteriorate, and you do all tasks more slowly and worse.

Studies have found that reduced work efficiency due to lack of sleep costs US businesses a huge amount. An average of $100 billion is lost per year.

Here's what George Belenki, director of the Center for Sleep and Performance Studies at the University of Washington, had to say about it:

If your job is mental, you pay productivity for lack of sleep.

After that, a completely logical question arises: how much time do you need to sleep in order not to accumulate fatigue and reduce productivity?

Based on research data, we can say that this time is from 7 to 7.5 hours. In general, experts agreed that 95% of adults need 7 to 9 hours of sleep per night to be productive.

For most adults, it is better to sleep 8 hours a day, and for children, teenagers and the elderly - even more.

How sleep works: sleep and wake cycles

The quality of your sleep is determined by a process called the sleep-wake cycle.

There are two important points in this cycle:

• Non-REM sleep (also known as deep sleep).
• REM sleep (REM phase, rapid eye movement phase).

During slow-wave sleep, the body relaxes, breathing becomes calmer, blood pressure drops, and the brain becomes less sensitive to external stimuli, making it harder to wake up.

This phase is of great importance for the renewal and restoration of the body. During slow-wave sleep, growth hormones are produced in the pineal gland, which provide tissue growth and muscle repair.

Researchers also suggest that the immune system is restored during non-REM sleep. So the slow phase of sleep is especially important if you play sports. Some professional athletes, like Roger Federer or LeBron James, slept 11-12 hours a night.

Another example of the impact of sleep on physical performance is a study conducted on basketball players at Stanford University. During the study, the players slept at least 10 hours per night (as opposed to the 8 hours of sleep they were used to).

The experiment lasted five weeks, during which the researchers assessed the speed and accuracy of the players in comparison with their usual results.

It turned out that just two extra hours of sleep increased the number of successful throws by 9% and reduced the time to sprint 80 meters by 0.6 seconds. So, if you have heavy physical activity, the slow phase of sleep will help you recover.

REM sleep is just as important for the mind as slow sleep is for the body. Most of the time when you sleep, the brain is calm, but when the REM phase comes, it becomes active. This is the phase during which you dream and your brain redistributes information.

During the REM phase, the brain erases unnecessary information and improves memory by linking the experiences of the last 24 hours with previous experiences, facilitating learning and provoking the growth of neural connections.

At this time, the body temperature rises, blood pressure rises, and the heart beats faster. In addition to this, the body is moving. In general, REM sleep occurs three to five times a night for a short period of time.

A person cannot function normally without both phases of sleep. Sleep deprivation affects health: immunity goes down, consciousness becomes “foggy”, the risk of infectious diseases increases, blood pressure and the risk of heart disease increase. In addition, sleep deprivation threatens mental illness and reduces life expectancy.

The slow phase of sleep helps restore physical health, the fast phase - mental capabilities.

However, despite the great importance of sleep for the body, the quality and duration of sleep during life change.

Age-related changes in sleep

Based on research from Harvard Medical School, it can be said that as people age, it becomes increasingly difficult to fall asleep. This phenomenon is called sleep delay. And sleep efficiency - the percentage of time you spend in bed while sleeping - is also decreasing.

On average, 80-year-olds have 62% less long sleep than 20-year-olds. There are many factors that affect the aging of tissues, and if this phase of non-REM sleep is shortened, the aging process is even faster.

Healthy sleep is your best weapon against rapid aging.

How to recover from lack of sleep

Most adults need 8 hours of sleep to keep their performance at their best. Since older people have trouble sleeping, they can make up for the lack of nighttime sleep by taking a nap during the day.

In any case, if you understand that you need to take a nap, it is better to do it once in the middle of the day than to periodically fall asleep during the day and evening.

In general, the body recovers well after short-term sleep deprivation. For example, if you had a rough night where you managed to get 2-4 hours of sleep, the next night 9-10 hours of sleep will completely restore your body.

It's just that your body will spend more time in REM and NREM sleep to make up for the lack of sleep last night.

There is no need to plan how much time your body will spend in REM and non-REM sleep. It knows better how much sleep and how much sleep is needed for recovery, so you will not be able to control this process.

And remember that there is no substitute for sleep. If you are bound to stay awake longer today, make sure you sleep longer than usual the next night.

circadian rhythms

How are your sleep and wake cycles organized?

With the help of circadian rhythms. These are biological cycles of different processes that occur within 24 hours.

Here are a few key points of the 24-hour cycle:

6:00 a.m. - Cortisol levels rise to wake up your body

7:00 am - melatonin production stops;

9:00 - peak production of the sex hormone;

10:00 - peak of mental activity;

14:30 - the best level of coordination of movements;

15:30 - best reaction time;

17:00 - the best work of the cardiovascular system and muscle elasticity;

19:00 - the highest level of blood pressure and the highest body temperature;

21:00 - melatonin begins to be produced to prepare the body for sleep;

22:00 - The work of the digestive system calms down, as the body prepares for sleep;

2:00 - deepest sleep;

Of course, these are only approximate rhythms, since they are individual for each person and depend not only on daylight, but also on habits and other factors.

In general, circadian rhythms are influenced by three main factors: light, time, and melatonin.

Light

Light is one of the most significant factors that sets the circadian rhythm. Staying in bright light for about 30 minutes can reset your rhythms, no matter what time it is.

In general, when the sun rises and light enters your closed eyes, it signals the start of a new cycle.

Time

The time of day, your daily schedule, and the order in which you are used to completing different tasks all affect your sleep and wake cycles.

Melatonin

It is a hormone that causes drowsiness and controls body temperature. Melatonin production depends on a daily, predictable rhythm. Its amount increases at night and decreases when it becomes light.

How to sleep better

Here are a few rules for falling asleep quickly and sound sleep.

Avoid caffeine

If you have trouble sleeping, it's best to eliminate caffeine from your diet altogether. But if you can't turn on in the morning without a cup of coffee, at least don't drink it after dinner.

Quit smoking

In the experience of many people who quit or have already quit smoking, cigarettes have a bad effect on sleep. After you quit smoking, it will be easier to fall asleep, the number of awakenings at night will decrease.

Use the bedroom only for sleep and sex

Remove the TV from the bedroom, do not bring a laptop and tablet. The ideal sleeping environment is a dark, cool, and quiet bedroom, so try to make it that way.

Exercises

Physical activity helps the body and brain shut down at night. This is especially true for older people. It has been proven that mobile, active older people sleep much better. However, at least three hours should pass between classes and sleep, so that the brain and body have time to calm down and prepare for sleep.

Temperature

Most people sleep better in a cool room. The ideal temperature in the bedroom is 18–21°C.

Sounds

A quiet room is ideal for a great night's sleep. But if you find it difficult to fall asleep in complete silence, you can turn on white noise.

No alcohol

Small (or very large) amounts of alcohol can help you fall asleep, but the quality of such sleep leaves much to be desired. During such sleep, the REM phase is reduced, so you do not have a good rest, even if you slept all night.

How to get ready for bed

Here's what to do to avoid insomnia.

Set a daily schedule

Our body loves systems. Basically, the circadian rhythm is your daily routine on a biological level. Go to sleep and wake up at the same time every day.

Get in the habit of turning off all electronics an hour or two before bed. Light from a computer, TV or smartphone delays the production of melatonin, which helps the body prepare for sleep.

In addition, working before bed increases brain activity and can increase stress levels, which is bad for sleep. Instead of checking your work email, read a paper book. This is a great way to get away from the screen and learn something interesting and useful.

Use relaxation techniques

Researchers claim that 50% of cases of insomnia are due to strong emotional experiences and stress. Find a way to reduce stress and you'll find it much easier to fall asleep.

Proven methods include journaling, breathing exercises, meditation, and exercise.

Don't miss the opportunity to take a nap

Afternoon naps help replenish sleep cycles. This is especially useful for those who cannot sleep well at night.

How to be more energetic in the morning

Drink a glass of water in the morning

Your body has gone 6 to 8 hours without water. Feeling sleepy in the morning (of course, if you slept enough) can be caused by a lack of moisture. So a glass of cool water may well refresh you.

Start your day in sunshine

Sunlight in the morning is especially important for the circadian rhythm. Light wakes up your brain and body so you don't even need your morning coffee during the sunny summer months. The main thing is to stay in the morning in the light.

Conclusion

So, the main idea of ​​this article is that nothing can replace sleep. If you quite consciously subject yourself to deprivation, you do not allow the brain to work to its fullest, and the body - to recover.

Lack of sleep is an obstacle between you, health and productivity. So sleep more.

Night rest accounts for about a third of a person's life, 7-8 hours a day. This physiological process contributes to the recovery of the body and goes through 4 or 5 successive cycles of fast and slow phases.

The first (it is also paradoxical) takes up to 15 minutes of time. The second - orthodox or slow sleep - lasts about an hour and a half, comes immediately after falling asleep, has 4 stages. The last, fourth, deep or delta sleep has the greatest effect on the body.

The Importance of Deep Sleep

Why is the delta phase important in the process of night rest? During the day, the brain receives and processes a huge amount of various information, and its memorization is carried out in the delta phase. That is, the effectiveness of training and the level of intellectual development directly depend on the quality and duration of deep sleep. In addition to transferring acquired knowledge from short-term memory to long-term memory, physiological processes are of great importance.

In the course of scientific research, it was found that the maximum relaxation of the muscles is noted in the deep stage. At the same time, catabolism slows down and anabolism, the restoration of body cells, is activated. Toxins and other harmful waste products are removed from it, immunity is increased.

Thus, a person fully rests precisely in the period of delta sleep. A change in its duration or a failure of the entire cycle leads to chronic fatigue, drowsiness, a weakened immune system, and a decrease in intellectual abilities.

Structure

Slow-wave and REM sleep alternate throughout the night cyclically. Falling asleep begins with the first, orthodox phase. It lasts about an hour and a half and takes place in four consecutive stages:

• A decrease in the alpha rhythm on the EEG, the appearance of low-amplitude theta rhythms. At this time, a person is in a state of half-asleep, which may be accompanied by the appearance of dream-like hallucinations. Thought processes continue, manifesting in the form of dreams and reflections on the events of the day. Often there are solutions to pressing problems.
• The electroencephalogram registers the predominance of theta waves, as well as the occurrence of characteristic accelerations of the rhythm - "sleep spindles". At this, the longest stage, consciousness turns off, the threshold of perception rises, but it is still possible to wake the sleeping person.
• The appearance of high-amplitude delta waves on the EEG. In the third phase of non-REM sleep (from 5 to 8% of the total duration), they take up less than half of the time. As the delta rhythm predominates, the deepest delta sleep occurs.
• In the fourth phase, which accounts for up to 15% of the night's rest, consciousness is completely turned off, it becomes difficult to wake the sleeping person. This period accounts for most of the dreams, while the likelihood of manifestations of disorders (somnambulism, nightmares) increases.

Orthodox sleep is replaced by REM sleep, the ratio is approximately 80% and 20%, respectively. In the paradoxical phase, a characteristic mobility of the eyeballs is observed, if the sleeper is awakened, he will remember a vivid dream of the sleep phase. The EEG shows electrical activity close to the state of wakefulness. Morning awakening occurs after 4 or 5 full cycles in the "fast" stage.

Normal duration

What is the rate of deep sleep? Its duration and quality are determined by the individual characteristics of the human body. One needs a 4-hour rest, the other will need at least 10 to sleep. The duration is also affected by the age of the sleeper: in childhood it is up to 9-10 hours, in youth and maturity - about 8, and by old age it is reduced to a quarter of a day. The average ideal time for a night's rest is 7 or 8 hours, and the rate of deep sleep for an adult is determined by the percentage of phases.

If we take 8 hours of sleep as a basis, the duration of the deep period in a healthy person will average 20%. That is, in general, it will take at least 90 minutes, and each of 4-5 cycles will take 20-25 minutes. With a reduction or increase in night rest, the time of each phase decreases or increases accordingly. However, their ratio in percentage terms does not change, and the body is fully restored.

Processes in the body

The electrical activity of the brain is described in the corresponding section on the structure of sleep. And how are all phases physiologically manifested? At the beginning of falling asleep, the muscles relax, the pressure and body temperature decrease, and breathing slows down. In the second period, these indicators increase, but it is still possible to wake a person, despite the partial shutdown of consciousness and an increase in the threshold for the perception of external stimuli.

The deep phase, which combines the 3rd and 4th stages, is normally characterized by complete relaxation of the muscles and a slowdown in all metabolic processes. It is difficult to wake up, and motor activity indicates the presence of disorders.

Causes of violations

Sometimes life circumstances require reducing the time of deep sleep (exam session or time pressure at work). Short-term or mental activity is quickly compensated. But if the duration of this phase decreases over time, chronic fatigue appears, memory deteriorates, and somatic diseases develop.

The reasons may be:

• psycho-emotional overload, stress;
• diseases of internal organs, nervous or endocrine systems;
• forced awakenings at night (with prostatitis to empty the bladder);
• arterial hypertension.

All these conditions require seeking medical help and treatment, since delta sleep is vital for a person.

How to normalize deep sleep

The deep sleep phase should be at least 20% of the total. If you have chronic feelings of lack of sleep, weakness and fatigue, it's time to think about how to increase the total time of sleep. It is important to follow the regime, try to stick to the chosen time for falling asleep and waking up. Physical activity during the day and a quiet environment in the evening, combined with a light dinner, also contribute to the normalization of sleep.

Learn the phases of sleep. There are four phases of sleep, the last of which is REM sleep. In order to increase the duration of the dreaming phase, the body and consciousness must gradually go through the first three phases. It is recommended to follow a regular sleep schedule and healthy habits in order to achieve your goal.

• First stage: In this stage there is a transition to sleep, which takes about five minutes. Eye movements under the eyelids slow down and muscle activity decreases, but a person can still easily wake up from extraneous noise or sound.
• Stage Two: This is the first stage of true sleep, lasting 10–25 minutes. Eye movement stops completely, heart rate and body temperature decrease.
• Third stage: This stage is the beginning of deep sleep, during which it is difficult to wake up, and if awakened, the person often feels weak or temporarily disorientated. At this stage, brain waves slow down and blood flow is directed from the brain to the muscles to restore the body's physical strength.
• Fourth stage: The last stage is the phase of deep sleep or dreams. It occurs 70-90 minutes after the person has fallen asleep. At this point, there are rapid eye movements, shallow breathing, an increase in heart rate and blood pressure. In this phase, the arms and legs are also paralyzed.
• Nighttime sleep follows a pattern with constant switching between deep and REM sleep. Each cycle lasts about 90 minutes and is repeated four to six times per night. Over time, the duration of each stage changes. The deepest sleep occurs in the first half of the night. After that, the duration of REM sleep increases.

Keep a consistent sleep schedule. You should stick to a sleep schedule where you go to bed and wake up at the same time every day, even on holidays and weekends. How much sleep you need varies from person to person, but on average, healthy sleep takes between seven and nine hours. A consistent sleep pattern will increase the frequency of REM sleep by switching between different stages several times a night.

Turn off all electronics and distractions a few hours before bed. It is recommended to turn off the TV, smartphone, tablet and computer, or remove all electronic devices from the room altogether. Screen lighting irritates the brain, inhibits the production of melatonin (which promotes REM sleep), and also affects the body's internal clock.

• Try shutting down your computer according to a schedule. Thanks to the schedule, the system will automatically go to sleep, and you will not be able to work too late or right before bedtime. Similar features are available for both PC and Mac computers. In addition, you can also configure the computer to wake up in the morning at the right time.