Sleep is a unique state during which all systems, and above all the brain, operate in a special mode. During this period, self-regulation of the body occurs, a deep shutdown of consciousness necessary for the natural restoration of strength and energy. Its average duration per day, determined by doctors for an adult, is approximately 7-8 hours, but it can vary depending on the individual characteristics of the body. Regardless of the rest mode, the cyclical pattern with a predominance of deep sleep remains unchanged.
How long should the deep sleep phase last?
The deep phase on average occupies 75-80% of sleep duration . The rest of the time is usually REM sleep. The phases replace each other several times during the night. During 8 hours of sleep this happens at least 4-5 times.
After falling asleep, the deep phase of sleep begins, which consists of 4 stages. After the end of deep or slow-wave sleep, REM sleep follows. By the way, the completion of one phase of deep sleep and one phase of REM sleep is called a cycle .
On average, one sleep cycle in a person lasts 90-120 minutes. If we take deep sleep to be 75% of the total sleep duration, it turns out that slow-wave sleep lasts about 65-90 minutes. Accordingly, the remaining 25-30 minutes fall into the REM sleep phase. In reality, REM sleep lasts less - about 10-15 minutes, and deep sleep - 75-85 minutes remaining from the cycle.
Considering that there are approximately 5 such cycles per night, we multiply the duration of the slow and fast phases by 5 and find that the total duration of deep sleep is approximately 400 minutes or almost 6.5 hours (with an 8-hour duration of total sleep).
In any case, exact numbers are difficult to know without special equipment that is used in sleep diagnostics. As morning approaches, the proportion of slow-wave or orthodox sleep in the cycle decreases, while the percentage of fast sleep phase increases. That is why it is very difficult to calculate the exact duration of the deep sleep phase without polysomnography .
Effect on the body
This type directly affects the body and its functions. It is responsible for endurance and thought process. This was found out through experiments with different people. It turned out that those people who slept more were able to remember more words.
During the tests it was found that if an individual is deprived of the opportunity to sleep for a long time, it will be equivalent to insomnia. In addition, it is not compensated for by additional sleep. Ultimately, in the absence of the normal course of this phase of sleep, a person may experience symptoms such as:
- deterioration of attention;
- memory loss;
- decreased ability to work.
Manifestations gradually provoke diseases of most organs.
Norm of deep sleep in children
During deep sleep, the child’s brain actively develops, so children need as much sleep as possible for intellectual development. However, in infants up to 3 months of age, the deep sleep phase is not observed. Instead, a normal restful sleep follows.
3 months after birth, nervous activity is activated, and with it deep sleep appears. In the first months of life, the duration of the slow phase is only 20-30 minutes . However, over time it increases to the physiological norm of an adult.
Norms
How long does sleep last? The duration of rest is individual. The number of hours depends on the age and state of his health.
Scientists have derived the average number of its normal course for children, adults and the elderly.
For children
The course of the stage is directly related to the development of the child’s brain. In infants, development has not yet occurred, which means that they do not have this stage. Instead, they have a restful dreaming stage. By 3 months of age, the brain begins to develop and a 20-minute deep phase appears.
Important! Children sleep more soundly than adults while in the second stage. They react less well to light, touch, temperature changes and other stimuli.
For adults
For adults, the normal duration in numerous experiments is 2 hours for people under 35 years of age and 1.5 hours for people under 60 years of age. Deep sleep and its norm for an adult are average and depend on the state of health and individual characteristics.
For the elderly
Pensioners over 60 years old, on average, should be in the deep phase for 80 minutes. Over time, this figure decreases and by the age of 80 reaches 50 minutes.
Deep phase in sleep structure
About 10-15 minutes after falling asleep, the deep sleep phase begins. At this time, restoration processes occur in the body: heart function improves, tissues are regenerated, and brain functions are normalized.
It is difficult to wake up a person who is in the slow phase of sleep. The reaction to external stimuli is minimal, so it can only be disturbed by loud sounds. Waking up in the slow or orthodox phase, a person will feel very drowsy. Especially if the duration of the current sleep was less than usual, that is, less than 7-8 hours.
Unlike the fast phase, during slow sleep the sleeper does not experience twitching of the arms or legs, there is no sleepwalking or talking in his sleep.
What it is
Scientists call the deep stage of slow rest, which is responsible for the process of restoring the body after a busy day. It occurs at night during rest. In science it is called slow-wave, orthodox or delta sleep. Its difference from superficial is a slowdown in brain activity, a decrease in muscle activity, and a decrease in sensitivity to odors and external stimuli.
Interestingly, researchers who studied deep sleep over a long period of time found that the brain does not rest when it sleeps. It processes the information received during the day. Thus, the brain is constantly functioning and the thought of resting during this sleepy stage is incorrect.
Stages of deep sleep
The deep sleep phase normally consists of 4 stages. Let's look at what happens to our body in each of them.
- Nap . The muscles of the body gradually relax, while the brain continues to react to external factors. You can talk to a dozing person, but he is unlikely to be aware of what exactly he is saying. In other words, drowsiness is a borderline state between sleep and reality.
- Falling asleep . During this period, consciousness turns off, but the person still reacts to external signals. At the same time, the heart slows down its rhythm and body temperature decreases. Sleep at the stage of falling asleep is very sensitive, so a person will easily wake up in the process of falling asleep if disturbed.
- The beginning of deep sleep . The brain switches to the delta rhythm, during which sleep occurs.
- Deep/slow-wave orthodox sleep . There is an increase in delta waves in the brain, due to which the body literally goes into a low-energy mode. During this period, the muscles are as relaxed as possible, and body temperature drops to the lowest possible level. The pulse and breathing rhythm slow down, and the brain does not respond to external factors at all. It is difficult to wake up a person who is in the delta stage of sleep. But if he wakes up, he will feel very weak and simply disoriented. In addition, most dreams occur in the delta sleep phase.
What else happens during deep sleep?
The stages of deep sleep and REM sleep differ from each other in the following ways:
- During slow-wave sleep, the body's metabolism slows down.
- During orthodox sleep, the activity of the sympathetic nervous system decreases. That is, the body is as relaxed as possible at this time.
- Deep sleep is characterized by a decrease in heart rate. In the fast phase, on the contrary, the pulse often increases, especially when having emotional dreams.
- In the slow phase, the production of adrenaline, cortisol and other stress hormones decreases. At the same time, anabolic hormones - testosterone and somatotropin (growth hormone) tend to a physiological maximum.
- In deep sleep, recovery processes in the body are more intense.
Also, the difference between REM and NREM sleep lies in their effect on physiological systems. For example, REM sleep is more necessary for mental health, while slow sleep is more necessary for the normal functioning of the body.
Sleep is an excellent healer, so to recover from illness or injury, doctors advise getting more sleep in order to recover from illness much faster
Recommendations
To increase the duration of the second phase, in addition to the above, you need to try to take a warm, soothing bath.
It is necessary to go to bed in a dark room and use warm bedding.
It is also recommended to play a soothing melody at night and saturate the room with the smell of pleasant incense in advance.
How to increase deep sleep phase
Ideally, it is better to sleep 8-9 hours a day. In this case, the duration of the deep sleep phase will be equal to 30-80% of the entire duration of rest. If slow-wave sleep is less than 30% of your total sleep, health problems may arise, such as heart function.
Health can also deteriorate when the deep sleep phase is extended. In this case, performance decreases and chronic fatigue syndrome often appears.
To increase the deep sleep phase, follow these recommendations:
- Maintain a certain sleep schedule . Go to bed and wake up at the same time. And even on weekends.
- Avoid drinking coffee, strong tea and other caffeine-containing drinks after 15:00 . Caffeine entering the body in the afternoon stimulates the nervous system. This in turn can shorten the duration of slow-wave sleep.
- Don't smoke or drink alcohol before bed . Nicotine and strong drinks reduce the duration of deep sleep.
- Finish dinner at least 3 hours before going to bed . Overeating at night interferes with good sleep. If you are hungry before bed, drink a glass of milk or fermented milk product. You can also eat 1-2 fruits at night, for example bananas, apples or pears.
- Meditate before bed . Spiritual practices help you relax, which in turn has a positive effect on sleep. Read about how to meditate correctly in this article.
- Play sports . In people who are “friendly” with sports, the deep sleep phase lasts longer compared to those who exclude physical activity.
- Create favorable conditions for sleep . The temperature in the bedroom should be in the range of 17-21 C. At the same time, to avoid freezing, sleep under a warm blanket. During the warm season, go to sleep with the window open. Better yet, buy an air conditioner and turn it on for a few minutes before going to bed. Also, sleep with the curtains drawn tightly and in complete silence. All of the above helps increase the duration and depth of slow-wave sleep.
It is worth saying that the duration of slow-wave sleep, no matter how much you increase it, will not last longer than the physiological maximum. For example, the delta sleep phase in a healthy person should not exceed 30% of the total duration of night rest.
Prolongation of the deep sleep phase, identified by the results of polysomnography, may indicate hidden health problems. For example, these could be diseases of the brain or endocrine pathologies.
By the way, lack of deep sleep has an even more detrimental effect on health. It has been experimentally proven that reducing the duration of orthodox sleep to a minimum can lead to dire consequences.
Deep sleep and its features
The night journey to the kingdom of Morpheus begins with immersion in deep slow sleep. Certain areas of the brain take part in its formation: the hypothalamus and its nuclei, the Moruzzi inhibitory center. The functioning of the systems slows down, the body partially switches off and goes into a state of deep rest and rest, tissue restoration begins, the formation of new cells and structures begins.
Structural elements
NREM sleep is called deep or orthodox sleep. Unlike the superficial one, it is divided into 4 main stages:
Nap. A person is already beginning to fall into a shallow sleep, but the brain is still actively working. Consciousness is confused, so dreams are often intertwined with reality, and it is during this short period that one can find a solution to some problems that were difficult during the daytime.
Falling asleep. The time when the main parts of the brain begin to switch off, but are still sensitive to any irritation from the outside. A person can easily be awakened by a loud noise, but it will take him some time to fall back to sleep.
Deep dream. A good period when the body relaxes as much as possible, all processes slow down, motor and brain activity is practically reduced to nothing.
Delta sleep. The person is completely immersed in an unconscious state. There is no reaction to external stimuli and sensitivity to odors. During this period, it is very difficult for the sleeper to awaken.
State of the body during deep sleep
The first stage is characterized by the following indicators:
- breathing slows down;
- body temperature decreases;
- heartbeat weakens;
- movements of the eyeballs are barely perceptible.
As you fall into a sleepy state, the pressure level decreases and the pupils become almost motionless. Blood flow to the tissue cells of organs and muscles increases, and growth hormone begins to be synthesized. At the last stage, there is a complete shutdown of consciousness, a reaction to external stimuli (bright light, noise, screams, singing), including no odors. The normal course of this stage allows you to remember some information after waking up.
Normal duration of the slow phase at different ages
It is known that deep sleep is a purely individual indicator, and how long it should last depends on the human body. So some people, like Napoleon, for example, need only 4 hours to get enough sleep. Others need at least 10 hours of sleep to maintain activity. Albert Einstein also belonged to this category.
According to the results of the experiment, which was conducted by specialists from the University of Surrey, it was found that the norm of sleep for each age group differs, which is clearly displayed in the table.
| Age | Total night rest/hours | Duration of slow-wave (orthodox) sleep/% |
| Newborn | 16-19 | 10-20 |
| Infant – 2-6 months | 14-17 | 10-20 |
| One year old baby | 12-14 | 20 |
| Child 2-3 years old | 11-13 | 30-40 |
| Children 4-7 years old | 10-11 | Up to 40 |
| Teenagers | At least 10 | 30-50 |
| Adults 18-60 years old | 8-9 | Up to 70 |
| Elderly over 61 years old | 7-8 | Up to 80 |
It is known that the norm of deep sleep in an adult exceeds the same indicators in children. Since the brain is just developing in infants at an early age, biological rhythms and processes have significant differences. As a result, orthodox sleep is of a minimum duration, which, however, tends to increase. Full formation of the structure ends by 2-3 years.
The Importance of Deep Rest
Depending on how long deep sleep lasts within one cycle determines how many hours per night the total duration is.
In the process of numerous studies, it was found that deep immersion in sleep has a tremendous impact on the mental abilities and physical development of an individual. Conscious reduction of the slow phase, even for several days, has a detrimental effect on a person’s well-being: his memory deteriorates, his concentration decreases, and his attention is distracted.
There are other differences that characterize the effect of deep sleep on the body.
- Complete restoration of strength and energy, tissue regeneration at the cellular level, calming and healing of the psyche.
- Unlocking intellectual resources, increasing work efficiency.
- Strengthening the immune system, increasing the body's defenses.
- Slowing down the aging process.
- Maintaining creative skills, concentration, and the ability to solve difficult life situations.
- Compensatory properties that help maintain good spirits and physical health.
Attention! Based on the above, we can conclude that a person’s health and well-being is directly dependent on the number of hours of slow sleep.
To ensure a good night's rest, you just need to train your brain to switch off from daytime problems, and your body to go to bed and get up at the same time.
NREM sleep disorder
Many people may suffer from intermittent sleep disturbances, but this does not have a negative effect on the body. Preparing for exams, completing an important project, preparing for a wedding and other life situations are factors that affect normal sleep and reduce its duration. A healthy body is able to compensate for lack of sleep over several nights. But if lack of sleep occurs over a long period, you should start looking for the cause of the dangerous disorder.
Causes
As practice shows, the most common factors that provoke insomnia in the adult population include the following:
- regular stress and nervous tension;
- mental disorders;
- hormonal changes in a woman;
- pathologies of internal organs, including the heart;
- endocrine disorders;
- diabetes;
- hypertonic disease;
- prostatitis or adenoma (in men);
- psycho-emotional overload.
It is important to know! A common cause of sleep disorders is common workaholism, when a person seeks to improve his well-being by reducing time for night rest. As a result, a vicious circle is formed - performance decreases, to increase it, the man or woman minimizes the period of sleep. As a result, the body suffers, but the financial situation does not improve.
Consequences
At a young age, as a rule, sleep disturbances are not as noticeable as in adulthood, but in everyone, without exception, they cause more severe disorders over time. Regular lack of night rest is bad for the body and leads to dangerous consequences.
- Deterioration in appearance: signs of fatigue, sallow complexion, bags and swelling under the eyes, the formation of fine wrinkles.
- Increase in body weight, development of obesity.
- Respiratory cessation and development of sleep apnea syndrome.
- Increased risk of heart attacks and strokes, development of cancer
- Decreased concentration, leading to difficulties at work and problems on the road.
- Deterioration of memory and ability to memorize, which affects the quality of life.
- The occurrence of various diseases due to weakened immunity.
All these problems arise due to a lack of deep sleep, so doctors advise changing your daily routine and increasing the time you rest at night.
What time does the deep sleep phase begin?
To determine the depth and duration of slow-wave sleep, it is necessary to undergo polysomnography. During the procedure, sensors are connected to the patient’s body that monitor the rhythm of breathing, pulse, snoring, movements during sleep and much more. The study itself takes place in special sleep centers, where a bed is prepared for you, on which sleep diagnostics are carried out during the night. Specialists will monitor your sleep and your condition during sleep. And the information obtained using polysomnography will help doctors more accurately understand the causes of poor sleep, if you have them.
However, not every locality has an office for polysomnography. In this case, trackers for tracking the phases of REM and deep sleep will come to the rescue. They look like a regular bracelet with built-in motion, heart rate and body temperature sensors. During the night, a device located on the arm reads 3 of these indicators. Then, based on the data received, the bracelet's microchip builds a graph on which the entire sleep structure is visible. You can view the graph on your smartphone by connecting the tracker to your phone via Bluetooth.
Unlike polysomnography, a sleep tracker provides imprecise data about your sleep. However, it is still able to show the overall picture of the dream. However, to find out the detailed structure of your sleep, you should undergo polysomnography, which will be prescribed by a sleep specialist.
Causes of poor sleep
Taking a long time to fall asleep, frequent awakenings at night and grogginess in the morning indicate the inadequacy of slow-wave sleep. Of course, the sleep situation can be improved, but first you need to determine the cause of poor sleep. Let's look at the main ones.
- Stress . Conflicts in the family or at work, stressful professional activities, states of shock and other similar factors can worsen the quality of sleep.
- Depression . Long-term depressed mood due to mental disorders is often the cause of insomnia.
- Chronic diseases . First of all, the quality of sleep is affected by hormonal levels in the human body. For example, thyroid pathologies can disrupt sleep. Moreover, endocrine problems may not manifest themselves in any other way.
- Uncomfortable posture during pregnancy . An enlarged abdomen in women during this period interferes with proper sleep. After the 12th week of pregnancy, sleeping comfortably on your side or back becomes more difficult. Therefore, expectant mothers have to adapt to physiological changes. Read about how to sleep during pregnancy here.
Of all the above reasons, stress has the greatest impact on sleep. If a person goes to bed with an unresolved and disturbing problem, sleep difficulties may arise. Anxious thoughts that appear in bed lead to painful and unsuccessful attempts to fall asleep. As a result, the duration of deep sleep is reduced, and in the morning a person feels sleep-deprived and tired.
Insomnia can be diagnosed if difficulty sleeping occurs for more than 5 nights in a row. But isolated and rare sleep disturbances are not classified as insomnia. However, if you cannot get enough sleep for more than 5 days in a row, consult your doctor.
In most cases, poor sleep is associated with frequent stress, moving and significant changes in life.
How to get rid of insomnia and normalize the duration of deep sleep
After determining the cause of poor sleep, treatment should begin. Depending on it, the doctor prescribes sleeping pills, prescribes psychotherapy/hypnotherapy, or refers to specialists in other areas to treat the primary cause of insomnia.
At the same time, the sleep specialist should talk about proper sleep hygiene, as well as how to deal with stress.
