What is Sleep Cycle And Why It Is Important To Know About It

Cycles, stages and rhythms of night’s rest

The phrase ‘sleep phases’ sounds beautiful and mysterious, intriguing with cognitive implications behind the succinct concept. You may have heard that sleep can be fast or slow, but you may not remember the intricacies of those definitions either. Since the quality of night’s rest is becoming more and more important every year, it is a good idea to re-learn the physiology of sleep phases and find out the difference between fast and slow sleep.

What are the Cycles of sleep

The scientific scheme of the human sleep structure comprises two main phases: slow sleep (aka slow wave, orthodox or Non-REM sleep) and rapid sleep (REM sleep, which is an abbreviation of the definition of “rapid eye movement” / rapid eye movement).

A healthy person’s sleep in a normal schedule according to biological rhythms is a cycle of two basic phases (each of which, in turn, has specific stages), repeated several times during the night. Human sleep has a different duration and specific functional tasks due to the activity of the brain’s structures.

How are the phases and cycles of sleep arranged

As we fall asleep we go to the slow phase of sleep, or to be more precise the first phase that lasts 5-10 minutes. This is actually the “prelude” to rest, the body’s transition from an active state to complete relaxation: breathing and pulse rate decrease, metabolism slows down, eye movements under the eyelids, temperature decreases, brain waves slow down and muscles relax (sometimes with impulsive twitching).

Then comes the second stage, which lasts about 20 minutes – a shallow or light sleep, during which muscle activity, temperature, heart rate continue to decrease, and the eyes stop moving. The light sleep phase, repeated like the others several times, takes about 45-55% of the total night’s rest time.

The third and fourth stages, deep delta sleep, take another 30-45 minutes each. The heartbeat and breathing goes to its slowest rhythm, brain waves and muscles are completely relaxed. It is during this period that the person is very difficult to wake up, he/she sleeps soundly and even if he/she talks in oblivion, does not remember anything afterwards.

The sleeping person then returns to the 2nd stage of slow sleep, which is followed by a first short session of REM sleep of approximately 5 minutes duration. This sequence of stages is called a cycle, the first of which is 90-100 minutes, and, on average, a healthy sleep lasts 4-5 complete cycles, depending on the age and needs of the body. Speaking of norms for a particular phase of sleep, it is worth noting that as cycles repeat, the proportion of slow sleep decreases and fast sleep increases.

Why the slow sleep phase is important

During slow sleep, and especially during the third and fourth stages, the body regenerates energy and physiological resources, triggering processes of cell regeneration, improving blood supply to muscles, and overall strengthening of the immune system. While we sleep soundly, the pituitary gland works, secreting important substances for the body, such as growth hormone, which promotes the development and regeneration of muscle and bone tissue.

Deep sleep also helps to structure the unrestrained flow of incoming information, allowing the brain to form conscious memories, supporting short/long term memory and general learning.

What happens during the rem sleep phase

Rapid or paradoxical sleep phase is characterised by increased brain activity, which is manifested by rapid eyeball movement spotted by researchers. Brain activity, as well as pulse rate, approaches the waking state during these minutes, and breathing becomes more rapid.

During REM sleep, the brain filters out information from the day, discarding unnecessary and unimportant information. Sleep scientists believe that those who wake up during the RBD phase are more creative and ready to tackle extraordinary tasks. And we also dream – 80% of dreams occur during REM sleep, and those who wake up during this period usually remember what they dreamt and describe what they saw in detail.

How to get a good night’s sleep given the phases of sleep

A quality night’s sleep is as important as a proper diet and regular workouts. Lack of sleep, scientists conclude, causes a wide variety of health problems – from overweight, pre-diabetes and depression to reduced immunity and sex drive.

The most effective method to ensure a sound and healthy sleep is to follow a regimen. Given your personal needs and knowing how many cycles of sleep phases your body needs to get a good night’s rest, determine the hour when you should wake up and when you should fall asleep, and follow this schedule by going to and from bed at the same time – every day and under all conditions.

Here are a few more tips to help you get enough sleep without disrupting your circadian rhythm and following the sleep phases that alternate clock by clock:

  • Exercise – at least 20-30 minutes a day, avoiding exercise a few hours before bedtime;
  • drink only water and beverages without caffeine in the afternoon – coffee, alcohol and nicotine make it difficult to get a good night’s rest;
  • Tune in after a long day – read a book or take a bath;
  • get rid of bright lights and loud noises in your bedroom: TV, laptop and preferably your smartphone;
  • if you can’t sleep, don’t lie in bed tossing and turning; instead, get up and do something quiet like read until you are sleepy again;
  • think about replacing pillows, blankets, buying soft and breathable bedding or rearranging your bed – perhaps you need a more comfortable nest to sleep like a baby.