Sleep phases: what they are and how they affect the body

Modern people are increasingly saving on sleep, devoting this most important time for recuperation to watching movies, working or night gatherings. But healthy sleep helps the brain reboot, strengthens the immune system and normalizes the psycho-emotional state. The condition of the skin, mood during the day, and the body’s resistance to stress and illness depend on it.

Sleep, as a physiological process, consists of two phases that are repeated 5-7 times per night. If the body does not pass them during a healthy night's sleep, fatigue, apathy and health problems may appear.

Human sleep according to the rules: sleep phases by the clock and their features

Sleep consists of slow and fast phases, alternately replacing each other. The duration of an individual stage ranges from one to two hours. In turn, the slow phase is divided into 3 stages. In general, our dream looks like this:

Aging and longevity

A series of articles conceived as part of the “biomolecules” special project for the Science for Life Extension Foundation.

In this series, we will consider the general problems of aging of cells and organisms, scientific approaches to longevity and prolongation of healthy life, the connection between sleep and aging, nutrition and life expectancy (let’s turn to nutrigenomics), we will talk about organisms with negligible aging, we will cover the topics of (epi)genetics of aging and suspended animation

Of course, the phenomenon of aging is so complex that it is too early to talk about radical successes in the fight against it or even a clear understanding of its causes and mechanisms. But we will try to select the most interesting and serious information about the discovered connections, model objects, developed and already available technologies for the correction of age-related disorders.

A brief summary of the special project is highlighted in the video “To grow old or not to grow old? // Everything is like animals.” You will learn more from our articles.

Stay tuned!

Circadian rhythms, and with them sleep, can be disrupted in anyone. It’s enough to stay late at the computer or fly a couple of thousand kilometers from east to west (or vice versa). A little earlier we talked about how mutations in the “internal clock genes” (and therefore sleep disturbances) lead to metabolic problems and, ultimately, can cause a variety of diseases. Interestingly, older people experience both sleep disorders and metabolic disorders at the same time. Most likely, this is somehow connected.

About the most valuable time for sleep and easy awakening

The most important recovery processes and restart of the central nervous system occur between 22:00 and 24:00. If you want to wake up rested and fresh, it is best to go to bed at this time. Going to bed after midnight is not recommended. Due to the lack of proper rest, the nervous system wears out faster, and irritability and nervousness appear.

It is best to wake up during the REM phase of sleep, when the body's sensitivity and activity increase. If you wake up at a slow stage, weakness and fatigue arise, which will accompany the person throughout the whole day. To calculate your ideal time to wake up, you can use a sleep sensor or fitness bracelet. These devices analyze your pulse, blood pressure and heart rate and tell you the time when you can get up.

To summarize, it is worth emphasizing that getting enough hours of sleep is important, but the quality of sleep should also be good. You can sleep for 8 hours straight and wake up completely exhausted. Therefore, a light dinner, less active leisure time in the evening, fresh air and lack of light in the bedroom are what will help you sleep not only for a long time, but also soundly.

Sleep and intelligence decline in old age

Sleeping is also important because during the slow-wave and REM stages of sleep, memory consolidation —the transfer of information from short-term memory to long-term memory [16]. The hippocampus plays a key role in this process. The information that a person received while awake is “played out” several times during sleep in the form of a sequence of electrical impulses in the cells of the hippocampus, and then transmitted to the cerebral cortex (mainly the prefrontal cortex), where it remains for long-term storage. The transfer of information from the hippocampus to the prefrontal cortex during sleep is facilitated because the concentrations of cortisol and acetylcholine [17] (substances that inhibit memory consolidation) in the brain are reduced (Fig. 2).

Figure 2. Age-related changes in the activity of signaling from the hippocampus to the cerebral cortex during sleep. As we age, the proportion of slow-wave oscillations in total sleep time decreases, the prefrontal cortex gradually degrades, cortisol levels increase and acetylcholine concentrations decrease.

[18]

In old age, the process of memory consolidation occurs with less intensity [18] due to three features that were already mentioned above:

the share of delta sleep in total sleep time decreases;
cortisol production increases;
The structure of the prefrontal cortex changes, its volume becomes smaller with age.

However, in older people who do not suffer from serious mental and intellectual impairments, sleep is no less important for memory consolidation than for young people. For example, both of these categories of people perform the task of remembering the location of objects better after sleep. The same cannot be said for older people with cognitive problems [19].

With motor memory the situation is somewhat different. Even in healthy older adults, sleep does not improve recall of a recently learned motor skill [20]. The exact reasons for this are unknown. Perhaps the fact is that in old age, memorizing sequences of movements deteriorates in any case, and against the background of this deterioration, the “help” of sleep in the memorization processes is not noticeable.

How to increase slow wave sleep?

Nowadays, many people prioritize efficiency and productivity.
Sleep deficiency negatively affects well-being, health, mood and ability to work. Therefore, in order to keep up with everything, everywhere, to be cheerful and positive, you should increase the duration of slow-wave sleep.

By following simple rules, you can get the most sound sleep at night and wake up rested and full of energy in the morning:

It is imperative to maintain a sleep schedule. Go to bed no later than 23-00. Only in this way will the duration of sleep be 8-9 hours. This time is enough to restore the energy spent during the day.
Sleep should cover the time period from midnight to five o'clock in the morning. melatonin is produced , a hormone responsible for our longevity.
If you can’t fall asleep early, take walks in the fresh air . Or take a warm bath with an infusion of relaxing herbs and sea salt.
A couple of hours before going to bed, try not to eat anything. Drink 200-250 g of warm milk. It is better not to drink drinks containing caffeine and alcohol in the evening.
Be sure to ventilate the room. Leave the window slightly open at night, but keep the doors to the room closed. You can also open the window in the next room. At night, the room temperature should not exceed +18 °C.
The mattress should be comfortable, it is advisable to replace the pillows with bolsters.
It is necessary to sleep in the dark. Melatonin, the hormone for sound sleep, is produced only in the dark. It is he who helps you sleep.
In the morning, after waking up, you should cheer up, for example, do exercises, swim in the pool or go for a run.

To wake up refreshed, track the ratio of the time you go to bed and wake up.
By following simple recommendations, you can increase the period of slow-wave sleep, thereby improving its quality.

We will also tell you:

Why do I have good dreams and nightmares?
What is lethargic sleep - fact or fiction?
How to get rid of drowsiness
How much sleep does an adult need?
Diet that fights insomnia

What does slow-wave sleep mean, and why is it important?

NREM sleep is a period when absolute relaxation occurs. Provided that a person sleeps no more than 9 hours a day .
If during this period he wakes up and feels tired and tired, most likely the problem is a lack of slow-wave sleep (SW).

Importance
Lack of slow-wave sleep can lead to health problems, for example:

the body's defenses decrease;
memory deteriorates;
new information is difficult to learn;
there is a large load on the nervous and endocrine systems;
The body slowly produces the necessary hormones.

Lack of sleep can cause heart disease, diabetes, dementia or Alzheimer's disease.

During the MS phase:

tissues are restored and muscles relax;
the brain is “recharged”;
memory structuring occurs;
blood pressure and temperature decrease;
breathing becomes calmer and less frequent.

This type of sleep comes in three stages. The stages of slow-wave sleep are designated by the Latin letters N. The first stage of slow-wave sleep (N1) or drowsiness is the bordering stage between the onset of sleep and wakefulness.

Ratio

At this time the following phenomena begin:

sleep paralysis;
sleepwalking;
sleep talking (somniloquy);
hypnagogic jerk.

The second stage, moderately deep sleep (N2) - the person falling asleep is completely disconnected from reality. Muscles relax and body temperature decreases. The duration of slow-wave sleep in the second stage is 20 minutes.

Stage III MS (N3) - deep sleep. Now breathing is rare, pressure is low. The body regenerates tissue, produces hormones and removes metabolic products. The brain generates memories at this moment. Now they are no longer short-term, but have been moved to long-term “archives”.

With the onset of the slow phase, strength is restored. A person, often waking up during this period, is deprived of the opportunity to “reboot” the brain.
As a result, he will feel unwell, will not be able to concentrate, nervousness will increase, apathy and irritability will appear.
With constant lack of sleep, there is a risk of serious mental pathologies.

Sleep and physiology