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.

  • Soma­totropin.

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.

Sleep and health: is it possible to deceive nature

Sleep phases

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.

Sleep and health: is it possible to deceive nature

Sleep rate

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.

Sleep disorders

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.

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