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How much deep, shallow and REM sleep do we need

A little more about the types of sleep and what happens to us during sleep.

If you sleep 7 to 9 hours - you spend about one third of your life asleep.

Sleep is very important to us. Reserves accumulate during sleep and the brain continues to process and organize what we have learned and experienced during the day so that we can use it in the future. Sleep is not static, its duration changes during a person's life. At the beginning of life you need more sleep, growing less and less.

Sleep is an important part of our overall health and quality of life. How well we sleep affects how well we feel awake. Both sleep duration and quality are important.


Sleep phases

Basically, sleep consists of two major parts - NREM sleep (non-rapid eye movement) and REM sleep (rapid eye movement). About 75 to 80% of the time we spend in sleep is in deep sleep, or more precisely in NREM sleep, and the rest of the time is in shallow sleep or (REM) sleep. Together, the two types of sleep form one sleep cycle. The average duration of the first NREM-REM sleep cycle is 70 to 100 minutes, and the second and subsequent cycles are approximately 90 to 120 minutes. These cycles can be repeated on average 3 to 5 times during sleep, if one of the cycles is interrupted, the next time you go to sleep, this cycle will be extended to compensate for the interruption.

The sleep cycle is further divided into stages or phases. Phases 1, 2, and REM are shallow sleep or (REM) sleep, and Phases 3 and 4 are deep sleep or NREM sleep.

Phase 1

We are sleepy and half awake during this time, so it is easy to wake us up at this stage. This is a shallow NREM sleep that will not last long. Muscle activity slows down and we can start dreaming, but moving to stage 2 can also cause a slight muscle twitch.

Phase 2

There is still a shallow sleep, but more stable - our breathing and heart rate slow down and the muscles relax. Our body temperature drops and the activity of the brain waves decreases.

Phase 3

We are entering a deep sleep or Delta sleep phase. This stage takes up approximately 3 - 8% of total sleep time. We breathe rhythmically and our muscle activity is significantly reduced.

4. Phase or Delta sleep

The deepest stage of sleep. During deep sleep, our breathing, heart rate, body temperature, and brain waves reach their lowest levels. Our muscles are extremely relaxed, and we have the hardest time waking us up and waking up, and it takes several minutes for us to fully recover. This stage takes about 10-15% of total sleep time. Walking and sleeping are also possible during this phase.

Phase 4 is known as the healing phase, when tissue growth and regeneration occurs, hormones that are important for the body's optimal functioning are released, and cell energy is restored.

Phase 5 or REM sleep

REM sleep is a time when we are most likely to dream. At this stage, our arms and legs are temporarily paralyzed to prevent us from physically fulfilling our dreams.

The first night REM cycle begins approximately 90 minutes after falling asleep and is repeated every 90 to 110 minutes during each sleep cycle. Our eyes move quickly behind our eyelids and our brain waves look like we are awake. Our breathing, heart rate and blood pressure rise almost to wakefulness.



Everyone dreams - about 2 hours every night, but you may not remember most of your dreams. The purpose of dreaming is unknown - it is believed that dreaming helps us to process emotions. The events of the day often take over our thoughts during sleep, and people who suffer from stress or anxiety are more likely to have frightening dreams. Dreaming is possible in all phases of sleep, but usually the most vivid are REM sleep. Some people dream of colorful dreams, while others only remember black and white dreams.


How long should I sleep in a deep sleep?

In healthy adults, on average 8 to 23% are spent in deep sleep for about 8 hours, which is about 62 to 110 minutes. However, as we get older, we need less deep sleep.

During deep sleep, the following functions occur:

  • Memories are consolidated;
  • What is learned during the day is strengthened (learning and emotion process);
  • Physical recovery is taking place;
  • Blood sugar levels are balanced;
  • The immune system is activated;
  • Balances metabolism;
  • Brain detoxification is performed.

If the period of deep sleep is insufficient - these processes do not take place or are not performed completely and symptoms of lack of sleep appear.

Symptoms caused by too long a deep sleep period have not been observed - it seems that there cannot be too much deep sleep.


How Much REM Sleep Do We Need?

There is no consensus on this issue. It is believed that during REM sleep we see dreams and experts believe that dreaming helps to process emotions and strengthen certain memories.

For most adults, REM takes up about 20 - 25% and appears to be healthy. However, sleep research raises some interesting questions. One recent study suggests that more REM sleep may be associated with depression, but it is not clear what causes it and what the consequences are.


How long should I sleep in shallow sleep?

Sleep researchers believe that shallow sleep is only good for us and does not have a minimum amount of time, because this phase of sleep is unavoidable, of course - if we sleep at all.

However, if you sleep too much regularly, you may have health problems. There are studies in which regular periods of long sleep are linked to obesity, depression, pain and heart disease.


How Much Sleep is Needed?

Our need for sleep and sleep patterns change with age and also vary considerably between individuals of the same age. There is no specific benchmark for the number of 'sleep hours' that would work for all people of the same age. Babies initially sleep up to 16 to 18 hours a day, which can promote growth and development (especially of the brain). School-age children and adolescents need an average of about 9.5 hours of sleep a night. Most adults need 7-9 hours of sleep a night, but after the age of 60, night sleep becomes shorter, shallower and more often interrupted by waking. Older people, however, are more likely to take medications that can interfere with sleep.

Long working hours and the availability of various daily entertainment shorten the natural sleep time required - we do not have time to sleep, we will go on holiday - however, it may turn out that we are not able to compensate for what is lost on weekdays and sleep disorders can start.

Recommended sleep duration




May be suitable for some


Not recommended



(0 - 3 months)

14 – 17

11 – 13

18 – 19

Less than 11

More than 19


(4 - 11 months)

12 – 15

10 – 11

16 – 18

Less than 10

More than 18

Little children

(12 years)

11 – 14

9 – 10

15 – 16

Less than 9

More than 16


(3-5 years)

10 – 13

8 - 9


Less than 8

More than 14


(6 - 13 years)

9 – 11



Less than 7

More than 12


(14 - 17 years)

8 – 10



Less than 7

More than 11

Young people

(18 - 25 years old)

7 – 9


10 – 11

Less than 6

More than 11


(26 - 64 years old)

7 – 9



Less than 6

More than 10


(≥65 years)

7 – 8

5 - 6


Less than 5

More than 9


How to improve sleep quality and sleep better

A person who falls asleep is less ill and his general health is improving - here are some tips to improve sleep:

  • Go to bed and get up at the same time every day.
  • Create a bedtime / sleep routine to help prepare your body and mind for sleep. This routine should include relaxing activities such as a warm bath, herbal tea, soothing music or a book, meditation, and more.
  • Exercise for at least 20 to 30 minutes a day, but no later than a few hours before going to bed.
  • Take a walk in the fresh air and sunlight for at least 30 minutes every day. Daylight is the main regulator of our daily sleep patterns.
  • Avoid caffeine, nicotine and alcohol for a few hours before going to bed.
  • Note healthy eating basic principles.
  • It is recommended to take the last meal no more than 2-3 hours before going to bed.
  • Avoid bright lights and loud sounds, keep the bedroom at a comfortable temperature (cool - ideally the room should be ventilated before going to bed.).
  • Eliminate all objects that make noise (even the watch if it makes it difficult to fall asleep).
  • Do not watch TV or use a computer (especially for work) for 30 to 60 minutes before going to bed.
  • Try to reduce stress - simplify your lifestyle, set priorities and delegate tasks to others - don't try to do everything yourself.
  • Avoid falling asleep during the day or at least limit it to 30 minutes or less.
  • If you can't fall asleep, do something like read or listen to music until you go to sleep.

If you have trouble sleeping or feel unusually tired during the day, see your doctor. Most sleep disorders can be treated effectively.



Sleep disorders and lack of sleep



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