Man throughout his history lives on a planet that rotates around its axis in 24 hours. At the same time, the planet revolves around the sun. Thanks to the combination of these two processes, we have day and night.
The human body has adapted perfectly to the daily change in the physical characteristics of the environment. The biochemical and physiological processes of the human body are subject to the change of day and night. Cyclic fluctuations in the intensity of body reactions are called circadian rhythms.
The body of any person on Earth — an “owl” or “lark”, an office worker with his five working days or an employee with a day-to-night job — is subject to the influence of circadian rhythms.
Sleep and hormones
Compliance with circadian rhythms is achieved with the help of hormones.
The main sleep hormone, which is mainly produced from 12 o’clock at night to 4 o’clock in the morning. At night, compared to daytime, its synthesis increases by 30 times. The peak is at 2 am. Melatonin regulates circadian rhythms, normalizes hormonal levels and blood pressure, affects the immune system, etc.
A growth hormone. Although the cycle of its production has a frequency of 4–5 hours, we receive the maximum amount of somatotropin during sleep, 1–2 hours after falling asleep. The hormone affects cell regeneration, accelerates wound healing, participates in the formation of bone tissue and strengthens the immune system. The sex hormone responsible for “male” reproductive functions and a host of other processes. The maximum output occurs during sleep.
Follicle-stimulating (FSH) and luteinizing (LH) hormones.
Hormones affecting the reproductive function of women and other processes. The maximum output occurs during sleep.
A satiety hormone produced by adipocytes (fat cells). With a lack of sleep, its production drops by 20%, and the less leptin, the stronger the feeling of hunger.
Hunger hormone that regulates appetite. If a person sleeps his norm of sleep, then the level of ghrelin in the blood plasma decreases — and the appetite weakens.
stress hormone. Normally, it maintains blood glucose levels during fasting and blood pressure during stress. When there is too little of it, our performance is at zero. When there is too much of it (during a stressful situation), we are abnormally active. But a long-term elevated level of cortisol is fraught with baldness, deterioration in the quality of the skin and blood vessels. During the day, we actively spend cortisol, and at night we restore it to normal.
One dream consists of several cycles, each of which takes an average of 1.5 hours. And each cycle consists of two main phases:
phase of slow sleep (deep sleep);
REM sleep phase (REM phase, “rapid eye movement” phase).
During the slow phase, growth hormone is produced, that is, the processes of tissue repair and growth, as well as the immune system, are activated. The brain is at rest during this time.
During REM sleep, the brain develops vigorous activity. This can increase body temperature, blood pressure and heart rate.
If a dream consists of several complete cycles, then a person (at the time of getting up) feels well-rested and rested. If you wake him up in the middle of any of the cycles, the sensations will be exactly the opposite, and the feeling of acute lack of sleep will haunt you all day. You can find out your cycle experimentally.
Why do you need sleep
Sleep is a time of “reboot” of the physiological functions of the body. This happens during non-REM sleep.
Sleep is a time for processing new information and organizing it, the processes responsible for memorization are actively working. This happens during REM sleep.
Sleep is a period of activation of the immune system. Sleep deprivation leads to increased production of granulocytes — white blood cells, indicators of the body’s stress state. Other studies have shown that during sleep, we also actively produce cytokines — small proteins that are necessary for the interaction between individual cells and entire body systems.
According to the calculations of the National Sleep Foundation, they talk about the following recommended sleep rates:
children under 1 year: up to 16 hours a day;
children aged 1 to 3 years: 12 to 14 hours a day;
children aged 3 to 5 years: 11 to 13 hours a day;
children from 5 to 12 years old: from 10 to 11 hours a day;
adolescents: 8.5 to 9.5 hours per day;
adults: 7 to 9 hours a day.
In adulthood, as we age, the duration of sleep also changes and the following changes occur:
sleep duration decreases;
the duration of slow (deep) sleep is reduced;
the time it takes to fall asleep increases.
Studies have shown that with age, the duration of the non-REM sleep phase, which we talked about above, is reduced by 62%. That is, less time and resources are allocated for the renewal of the body, which accelerates the aging process. Older people and middle-aged citizens fall asleep worse, and sleep a little less and not as soundly as young people. Alas, in life, everything is arranged the other way around: the young, who need more sleep, are desperately sleep deprived due to the hectic pace of life; but the old people toss and turn from side to side, unable to wait for the morning.
The norm of sleep should be respected — as far as possible. Sleep is such an amazing process that it shouldn’t be too little, but it shouldn’t be too much either.
Lack of sleep is fraught with a failure in the production of hormones, that is, it is a significant factor in the disruption of the immune system, the risk of developing obesity, diabetes and cancer. Scientists associate the latter with a reduced level of melatonin.
An excess of sleep also confuses the body and also causes hormonal disruptions. Result: obesity, diabetes, depression and cardiovascular disease (in women, an extra 2–3 hours of sleep increases the risk of developing heart disease by 38%).
Or maybe you can fulfill the norm of sleep, but without taking into account day and night?
Unfortunately no. Circadian rhythms are such an ancient acquisition of the Homo sapiens species that it is impossible to change them in the unfortunate 70–100 years of a person’s life, even if you start doing it from birth. Therefore, any deviations from the “day-night” cycle sooner or later lead to failures of all cyclic processes associated with it. That is, working at night, shifting schedules, day-night mode, regular business trips to a different time zone, and any other variations of the traditional lifestyle provoke disturbances in the production of hormones associated with sleep.