Sleep phases are the temporal and functional periods into which sleep has been divided by researchers. By and large, an ordinary person existing in the “wheel” of life does not care whether these phases exist or not.
However, sleep functions directly affect the state of the human body. This is both health and life expectancy. It is precisely because of the importance of sleep quality that world medicine invests huge amounts of money in sleep research.
Sleep is an unusual state of the body that is sometimes compared to death. In fact, they have little in common. In contrast to the complete death of the body, rest, on the contrary, promotes long life. It renews all systems, helps restore physical and moral strength.
At the same time, sleep is not something homogeneous in structure. There are different phases of sleep, each of which performs a specific function and lasts a very specific amount of time. Everyone knows that deep sleep is beneficial. But when it occurs, how it affects the body - only a few know about it.
Sleep phases and their characteristics
Sleep is divided into several stages (phases). They may repeat themselves during the night. One cycle lasts about one and a half hours. It consists of two phases:
- Slow (long) phase.
- Fast (short) phase.
The phases of sleep differ in their physiological characteristics.
Slow phase
It consists of several stages, each of which is launched sequentially, gradually introduces the body into a state of complete shutdown, and then returns it to a state close to awakening.
When falling asleep, a person goes through the following stages:
- Nap.
- Light sleep.
- Deep dream.
Napping is a short phase, about 10–15 minutes, that represents a smooth transition from wakefulness to sleep.
Light sleep is characterized by the beginning of a complete “shutdown” of the body. During this period, muscle activity decreases and heart rate decreases. During the stage of light sleep, body temperature decreases. The brain stops responding to external stimuli. The only thing that connects a falling asleep person with reality is hearing.
During the period of light sleep, a person reacts to sounds produced and may wake up from them.
Deep sleep is characterized by a complete shutdown of the body. During this period, the person does not react to external stimuli. The eyeballs, which up to this point were moving, almost lose this ability. At the stage of deep sleep, the energy spent during the day is completely restored, and the body’s protective functions are increased.
During deep sleep, a person sees many dreams, but the brain does not have the ability to remember them. Awakening at this stage ends in lethargy, bad mood, and low performance.
Some researchers include a delta stage between the stages of light and deep sleep, during which there is an intermediate period of slowing down of body functions. When conducting studies on the encephalogram, the waves at this moment have a deltoid shape.
Giving a general description of the deep sleep phase, it should be said that during the period of sound sleep, all physiological functions occurring in the body slow down. It is three times longer in duration than the fast one. At this stage, complete restoration of the body occurs, including at the cellular level.
Fast phase
It is three times shorter than the previous one. Includes two stages:
- Transition to REM sleep.
- Actually REM sleep.
The first is similar to light sleep from the slow sleep phase. The difference is that the processes that were slowing down are now activated:
- heart rate increases;
- breathing becomes more active;
- brain function is activated;
- a person’s reaction turns on;
- the movement of the eyeballs becomes sharp.
Man is approaching awakening.
If you wake up during this period, you are guaranteed a cheerful state, high performance, and a good mood. During this period he also sees many dreams, but unlike the stage of sound sleep, they are remembered.
Depending on the duration of the night's rest and the repeating nature of the phases, the duration of the stage of REM sleep itself becomes longer each time. If the first time it is short, about 15 minutes, then by the morning it can reach one hour. Accordingly, choosing a more precise time to get up is easier in the morning.
How the phases alternate
It has been scientifically proven that the phases change in a strict order, starting with the slow one. Also constant is the order of stages within each period. Only their duration changes. The stage of drowsiness falls out of the cyclical pattern; it occurs only in the first cycle or if the person wakes up.
One cycle - slow (3/4) and fast (1/4) phases. On average, a person sleeps 8 hours a day, the duration of one cycle is approximately one and a half hours, the number of phase repetitions will be 4–5 times. Exact calculations are made individually, depending on the total duration of rest.
The sequence of phases may be disrupted when a person has mental problems or is in a state of depression at the observed moment. For example, the stage of deep sleep may fall out, which negatively affects the general condition of a person.
Duration of the Orthodox phase
Today, people sleep less than they should, but still worry about their health. For this reason, doctors are increasingly hearing questions about how long deep sleep should last.
In fact, rest standards vary from person to person, although there are generally accepted standards. In general, the duration of the slow phase should be about 30% of the total sleep time. A significant decrease in this indicator will lead to memory problems, but an increase threatens the appearance of symptoms of prolonged sleep, that is, a person will wake up already tired.
Measuring the Duration of the Orthodox Phase
Accurate measurements are taken by medical equipment. However, such devices take up a lot of space, are expensive, and their use cannot be called convenient. For private use, sleep trackers have been created that allow you to determine the resting phase based on heart rate and frequency of movements.
The bracelets look stylish and are easy to use, although the measurements are subject to error. When combining their work with a smartphone, the data is transferred to the mobile device and stored for the required time. As a result, the duration of deep sleep is known and statistics are tracked based on the collected information.
Some trackers only show the total duration of the orthodox phase per night, while more advanced devices display the phase cycle throughout the entire measurement time. Naturally, the price of second-generation models is much higher.
A person determines the need to purchase a tracker independently, based on the presence or absence of sleep problems. If you just want to monitor your health and sleep quality, then a simple device will do.
In cases where insomnia or other problems with rest are diagnosed, a semi-professional tracker is necessary for the reliability of data collection.
Increasing the duration of deep sleep
Deep sleep is the phase from which the entire cycle begins, so a person cannot skip it. However, the reduction in the total rest time occurs due to this period in one of the cycle revolutions. As a result, there is a significant deterioration in well-being, bad mood in the morning and decreased immunity.
If such signs are detected, it is necessary to increase delta sleep. To do this, it is enough to follow a number of rules:
- Strict control over the time of falling asleep and waking up - you need to rest every day at the same time.
- Eat no later than 3-4 hours before going to bed. It is permissible to drink water or limit yourself to a glass of kefir. This measure is due to the fact that the body is forced to digest food instead of resting, and all active processes occur in the paradoxical phase.
- Complete rejection of bad habits helps to cleanse the body and normalize all processes. Alternatively, avoid smoking, caffeine and alcohol 4-5 hours before resting.
- Increasing physical activity will naturally prolong deep sleep because the body will need more time to recover.
- Meditation is relaxing. For some, these are sounds or aromas, while for others it is enough to sit for a few minutes in silence, throwing away all thoughts.
- Maintaining normal conditions in the room - temperature and humidity are regulated by household appliances. This will avoid sudden awakenings.
A few years ago, scientists advised people who have trouble falling asleep to listen to the sounds of nature. However, now medical statistics show that some patients who have lived in the city all their lives cannot fall asleep without the sounds of cars, especially when moving outside the city for permanent residence.
The delta is increased only to adequate values, that is, no more than 30% of the total rest duration. Further adjustment of indicators will only have a negative effect on the body.
Human sleep phases by time - table
To know exactly what time you need to wake up and feel cheerful, full of strength and energy, you need to calculate the duration of each stage. The studies carried out established the average values for each phase.
In the slow mode the duration is 10, 20 and 90 minutes, in the fast stage - 20 and 40 minutes according to the stages.
Based on these figures, a table is compiled indicating
- bedtime,
- duration of each phase,
- rise time.
With the right calculation, you will always feel cheerful and rested.
A more accurate time for the duration of sleep phases can be found out with the help of your loved ones, who will conduct individual observations, or undergo an examination and draw up an encephalogram.
The value of sleep
There is an opinion that sleeping in earlier hours, for example, from 21:00 to 2:00, is more important for health. There is a picture floating around the internet and social media pages showing that sleeping until midnight is the most effective. Allegedly, one hour of such sleep is equal to 2-5 hours of sleep after midnight. It is indicated that sleeping after 6 am does not make sense.
Of course, such information is not accompanied by any research. Yes, and logically this can be questioned. It turns out that if you go to bed in the morning, even a 10-hour sleep will go down the drain?
In fact, the lack of daytime sleep lies not in the hours, but in the fact that the rest occurs during daylight hours. At night in the dark, the brain produces melatonin , a sleep hormone that is very important for the full recovery of the body. Melatonin normalizes the duration of sleep phases, maintains sleep depth and speeds up falling asleep. When there is light, this hormone is produced worse, so sleeping in a lit room is not a good idea. If you constantly sleep in a light-filled bedroom, the quality of your rest may deteriorate.
The body doesn't care what time it is. For him, the level of illumination around is much more important. The darker the better for sleeping.
To summarize, let's say that the quality of sleep is weakly dependent on the clock. Much more important is the lack of light in the bedroom and the duration of sleep itself.
Why is the sequence of phases disrupted?
In healthy people, the sequence of phases and stages of sleep is specific and does not change. You can always set the exact time of going to bed and getting up. Changes are observed in young children and the elderly. The daily sleep duration of infants is 15–20 hours per day, and in older people this figure is reduced to 4–5 hours per day.
For these age categories, it is recommended to maintain a calm environment in the house so that awakening occurs naturally and does not cause nervous tension.
It is more difficult when an adult suffers from insomnia and is in a state of depression. In these cases, REM sleep becomes longer, leading to frequent awakenings. In this case, the period of deep sleep is significantly reduced or completely disappears. Such disorders do not allow the body to fully recover. The consequence of lack of sleep is emotional excitability and energy exhaustion, which negatively affects the mental and physical state.
Scientists distinguish three groups of sleep disorders:
- Presomnic.
- Intrasomnic.
- Post-somnia.
In each individual case, this is determined by a specialist during an examination. Most often, disorders are caused by a tendency to stop breathing during sleep and a sudden transition to the awakening phase.
More information about sleep stages in the video:
Causes of deep sleep disorders
Within one or two nights, a person’s sleep disturbances may not have any serious cause and will go away on their own. However, if violations persist for a long time, then there may be very serious reasons behind them.
- Changes in the psycho-emotional sphere of a person, and, first of all, chronic stress lead to persistent sleep disturbance. As a rule, for such psycho-emotional overstrain there must be some kind of psycho-traumatic factor that led to disruption of the process of falling asleep and the subsequent onset of the delta sleep phase. But sometimes these are mental illnesses (depression, bipolar affective disorder, etc.).
- Diseases of the internal organs play an important role in the disruption of deep sleep, since the symptoms of diseases can prevent a person from fully resting during the night. Various pain sensations in patients with osteochondrosis and traumatic injuries cause constant awakenings in the middle of the night, bringing significant discomfort. Men may have frequent urination, leading to frequent awakenings to go to the toilet. It is best to consult your doctor regarding these issues.
However, most often the cause of problems falling asleep is related to the emotional side of a person’s life. It is the causes of this group that occur in the majority of all cases of sleep problems.
Sleep duration - age restrictions
The average sleep duration for a healthy adult is 8 hours. In infancy, adolescence, and adolescence, there are different standards. A similar situation occurs with older people.
Considering different age categories, we can determine the average indicators for each of them.
- Children in their first year of life spend up to 20 hours a day sleeping.
- From one to three years old, babies need about 14 hours of sleep.
- For preschoolers, up to 12 hours will be enough.
- Primary school students - 10 hours. Sometimes you can increase the duration of sleep to 12 hours so that the child can fully recover from increased stress.
- Teenagers are treated the same as adults. Their sleep duration is 8 hours. In some cases it can be increased to 10 hours.
- Elderly people are recommended to sleep at least 7 hours a day. Constant lack of sleep has a negative impact on your health.
It should be noted that the numbers are not strict standards. It all depends on the individual characteristics of the body.
Features of awakening in each phase of sleep
You can wake a person in any phase or stage of sleep, but this fact will affect his well-being and emotional state throughout the day.
It is optimal to wake up during the REM stage of sleep. During this period, the body is completely ready for vigorous activity. The organs of hearing and smell respond to external stimuli. Waking up during this period, a person will be cheerful, active, and in a good mood.
In the slow phase of sleep, the activity of internal organs is inhibited. The person does not respond to sounds, does not smell, and has a slow heartbeat. Waking up during this period will lead to the fact that a person will be in such a inhibited state throughout the entire working day. To restore functionality, he needs to fall asleep again and go through the full cycle (slow and fast phases). Waking up in the latter will return you to your normal alert state.
NREM sleep is a period when the body recuperates
If we talk simply about what deep sleep is, then we can say that it is a kind of time for brain maintenance. The slow-wave sleep phase is accompanied by the elimination of various toxins and restoration of brain structure. At least, some scientists share this opinion.
As confirmation of the corresponding fact, it is given that if a person is deprived of the opportunity to remain in the corresponding phase, then his state will be the same as in which he would have been if he had not slept at all. That is, lack of deep sleep is accompanied by:
- Changes in sensory perception;
- Drowsiness and apathy;
- Impaired thinking and speech;
- General deterioration in health, etc.
When is the best time to wake up?
Based on the description of the state of the body in each phase, it is easy to conclude that it is better to wake up during the REM stage of sleep. A simple calculation will help you determine the time of its onset. The average duration of each stage will help determine the duration of one cycle. By multiplying the result by the desired number of repetitions, you can calculate the optimal time to wake up at which to set the alarm.
