How and how much you need to sleep to be healthy

Sleep is indispensable for the body. It “reboots” the brain, triggers recovery processes and stimulates the immune system. It is during sleep that brain cells replenish glycogen reserves – a structure that stores energy. But in order for all these functions to work properly, you need to sleep properly. How long and at what time to do it, whether it is possible to “catch up” lost sleep on the weekend and what threatens frequent lack of sleep – says a psychiatrist-narcologist.

How much sleep do I need to be healthy?

The total duration of sleep largely depends on age. So, according to a 2-year study by scientists of the National Sleep Foundation of the USA, each age group meets its own recommended “healthy” norm:

  •  Newborns 1-3 months − 14-17 hours
  •  Infants 3-11 months – 12-15 hours
  •  Children 1-2 years old – 11-14 hours
  •  Children 3-5 years – 10-13 hours
  •  Children 6-13 years old – 9-11 hours
  •  Teenagers 14-17 years old – 8-10 hours
  •  Adults 18-65 years old – 7-9 hours
  •  Elderly over 65 years – 7-8 hours

At the same time, sleep experts recommend counting sleep time not just for hours, but in cycles.
Our sleep is divided into 5-6 cycles with a length of 90-100 minutes. Each interval includes several stages. The first lasts 10 minutes, the second 20 minutes, the third 35-45 minutes, the fourth 20 minutes, and the last 5 minutes.

How much sleep do I need to be healthy

For the normal operation of sleep functions, it is important not to interrupt the cycle. Therefore, it is worth planning your sleep so that the total time is divided into 90 minutes.

That is, if the norm of healthy sleep for an adult is 7-9 hours, then it is worth going to bed for 7.5 and 9 hours.

But it is impossible to sleep more than 9 hours – according to another large-scale study by somnologists, this increases the risk of premature death from the development of cardiovascular and other somatic diseases by 30%.

At what time is it better to sleep?

A healthy time to sleep is determined by our circadian rhythms. These are changes in the intensity of biological processes of organisms associated with the change of day and night.

So, the human biological clock is “sharpened” for a 24-hour cycle. And in the period from 23 to 3 a.m., the pineal gland of the brain produces the “sleep hormone” melatonin. This substance performs a number of important functions:

  •  Controls daily and seasonal biorhythms
  •  Has a mild hypnotic and analgesic effect
  •  Regulates body temperature, respiratory rate, blood pressure
  •  Triggers regeneration processes and slows down aging
  •  Reduces stress
  •  Reduces fat and increases muscle size
  •  Has an anti-cancer effect

After 2 a.m., melatonin levels gradually decrease. And after 3 o’clock in the morning, the adrenal glands begin to produce cortisol – the so-called “hormone of vivacity and stress”, which speeds up the heartbeat, increases blood pressure and vascular tone. At 6-7 o’clock in the morning, the peak of cortisol concentration occurs. Also at this time, serotonin is actively produced – the “good mood hormone”, which makes it easier for us to wake up.

Therefore, the optimal sleep schedule is falling asleep before 23 o’clock (at about 10 pm) and waking up at 7 am.

Is it possible to sleep during the day? Why is it harmful to sleep in the evening?

The “nocturnal” production of melatonin is largely related to its sensitivity to light – especially sunlight.

In the retina of our eyes there are special ipRGCs cells that detect the presence of light sources. And only if we sleep in complete darkness, they send a signal to the epiphysis to produce a “sleep hormone”.

Because of this feature and the established rules of circadian rhythms, daytime and evening sleep cannot be a full-fledged replacement for nighttime sleep.

However, daytime sleep can help a person to “reboot” the brain with severe fatigue. To do this, it is better to lie down for a short time – for 15-20 minutes or an hour.

But this short-term rest should be carried out no later than 16 o’clock in the evening − because of the proximity to the night, evening sleep “interrupts” a healthy schedule too much. The body cannot adapt to the change, and as a result, either the night passes sleepless, or a person sleeps evening and night without waking up – and exceeds the healthy norm.

What about those who work at night?

Usually, after night shifts, a person has 1-2 free days off. In this case, you should go to bed immediately after coming home from work. But no longer than 3-4 hours – in this case you will be able to rest a little, and by the evening the desire to sleep will return, and a healthy night’s sleep will not be “interrupted”.

Also, if possible, it is worth taking short-term sleep breaks during work – 15-20 minutes or an hour.

If, due to the specifics of your work, you are forced to work regularly at night without intermediate “weekend” days, you should at least clearly adhere to a stable sleep schedule and ensure complete darkness during the daytime – for example, with the help of dense curtains and eye masks.
In case of sleep disorders, patients with a nighttime work schedule may also be prescribed melatonin-based medications.

How to go to bed and get up during holidays and weekends?

On weekends and holidays, many people try to “sleep off for the future.” Indeed, after a long working lack of sleep, such days help to improve your well-being a little.

But we already know that exceeding the norm of sleep – more than 9 hours – is harmful to the body, as is a violation of the schedule for the production of melatonin with cortisol.

What about those who work at night

Therefore, even during weekends and holidays, you should stick to a healthy schedule and sleep not “in advance”, but according to your age norm.

What do frequent sleep disorders lead to?

When, due to work, holidays, watching TV shows and other external reasons, we knock down a healthy sleep regime, this inevitably leads to future lack of sleep. The problem grows like a snowball: you go to bed later than 12 at night, wake up broken and try to “catch up” during the day or in the evening, at night you go back to bed later than you should because of insomnia after a nap. And the next morning you get up or later than you should on the day off (and the next night you fall asleep again naturally later), or you get up early in the morning for work and do not get enough sleep.

And lack of sleep is an extremely dangerous condition for all body functions.

So, scientists-somnologists note the concept of “nuclear sleep” – 6 hours. This is the minimum that is necessarily needed to maintain the functions of the body. Less time causes disorders of the psyche and internal organs.

Consequences of frequent lack of sleep:

Cardiovascular diseases

With less than 6 hours of sleep, the bone marrow overly actively produces immune cells that absorb cholesterol. This leads to an acceleration of the proliferation of atherosclerotic plaques due to cell redundancy. And vascular atherosclerosis, in turn, leads to the development of cardiac arrhythmias, ischemia, and an increased risk of myocardial infarction.

Reduced immunity

During sleep, the immune system produces cytokines – proteins that protect the body from inflammation and infections. With a lack of sleep , the amount of cytokines decreases .


With a lack of sleep, the ability of the hormone insulin to regulate glucose levels decreases. Therefore, chronic lack of sleep can lead to a prediabetic condition and cause type 2 diabetes.

Weight gain

With a lack of sleep, the body compensates for energy losses with the help of increased production of the hunger hormone ghrelin. As a result, with frequent lack of sleep, a person’s appetite increases and the risk of developing obesity increases significantly.

Deterioration of brain function

With a lack of sleep, the processes of processing new information and recovery in the structures of the brain are disrupted. Because of this, cognitive functions suffer – thinking, memory, and especially mindfulness. And this causes not only a decrease in productivity at work and school, but also accidents and road/work accidents.

Increased anxiety

Lack of sleep causes disturbances in the medial prefrontal cortex of the brain, which helps control anxiety, and causes excessive activity of the amygdala and other departments responsible for emotional reactions. The result is increased anxiety, irritability, aggressiveness, low self-control.


With a disrupted sleep schedule and frequent lack of sleep, circadian rhythms are disrupted, and they are closely related to the production of serotonin (the “hormone of happiness”) and other neurotransmitter systems that reduce stress levels. The result is a high risk of depression .

Decreased libido

In men, with lack of sleep, the level of testosterone and sex hormones decreases by at least 10-15%.

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