REM Sleep: Why is it important?

REM Sleep

Suppose you believe that nothing happens in your body and mind while you sleep. In that case, you are wrong: sleep is the biological activity of vital importance to our physical and psychic balance. It is totally indispensable for us to face a new day with our fully restored faculties.

Although even today, the function of sleep remains an unsolved biological mystery, great advances in its research have allowed us to understand the different brain mechanisms that control it.

If you already know the sleep phases, today we will take it a step further to delve into the most important stage, the REM phase.

As we sleep, we go through different phases of sleep that is divided into 2 large groups and repeated several times during the night: the first phase without rapid eye movement (not MOR) and another with rapid eye movement (MOR). However, they are usually better known by their acronym NREM and REM, respectively.

NREM Phase

The NREM phase represents 80% of an adult’s total sleep time and is divided into 4 deeper and deeper phases:

Phase I: it is a stage of numbness in which you get out and enter sleep with relative ease.

Phase II: sleep, although light, is getting deeper and deeper. Muscle tone decreases, eye movement stops and brain waves slow down.

Phase III: it’s the stage we really rest on. Also, it is in which sleep disorders, sleepwalking, night terrors and nighttime incontinence can occur.

Phase IV: in this phase is where deep sleep occurs and where our body is physically and psychically restored.


REM phase

It is the V stage and represents 20% of the dream. Approximately 70-90 minutes after we fell asleep, we entered this phase for the first time. The complete sleep cycle, i.e. from the starting stage, I to reach the REM stage, lasts between 90-110 minutes. Usually, throughout the night, we have 4 or 5 cycles in which the different phases alternate sequentially.

What is the REM sleep phase, and what happens in it?

During the time we spend in this phase (usually about 5 cycles of about 10 minutes), the presence of great brain activity is detected that we manage to perceive from the rapid and constant movements of the eyes.


You knew that…
This brain activity is very similar to that we have in a state of wakefulness or the sleep phase, so at this stage, it is also known as out-of-sync or paradoxical sleep.

The body remains motionless and, except the eyes and diaphragm, muscle tone disappears.

It is at this stage that dreams and nightmares appear as well as the ability to remember them.

Despite muscle atony, while we sleep, there is a great physiological activity in the body: it increases blood pressure, heart rate and respiratory, and other body reactions such as erections also appear.


What is the function of the REM phase of sleep?

Although there are still many questions about the functions of this stage of sleep, it is considered that while we remain in it, there is the reorganization of our perceptions and mental content to turn our experiences into memories, which are stored in long-term memory.

Likewise, at this stage is when there is a significant increase in the level of development of our brain. Therefore, it acquires the role of special relevance for the maturation of the brain during the growth stage.


How does REM sleep vary over a lifetime?

As we get older, sleep cycles change considerably, and we need to sleep more or fewer hours:

  • newborn spends most of his or her sleep time and, about 50% of his or her rest, is in the REM phase.
  • Starting at 4 months, a baby sleeps staggered about 14-16 hours and rem sleep time drops to 40%. As the child grows, rest patterns stabilize and, at about age 6, their cycles resemble those of a young adult.
  • Young adults sleep on average between 7 and 8 hours, 20-25% of which are REM.
  • In an older adult, especially from the age of 60, the sleep pattern is greatly reduced, and this includes REM-type sleep which, although decreasing, takes less time to appear.


Sleep behaviour disorder in the Rem phase

No total loss of muscle tone characterizes REM sleep behaviour disorder.

Those who suffer from it experience dreams and violent movements in the first person in a way that is very vivid and in which people or animals threaten them and, in response, shouts, insults, kicks and strikes indiscriminately with arms and legs.

This disorder usually occurs within 90 minutes of falling asleep, although it can be repeated throughout the night.

It can occur at any age but occurs most often in men over 60 years of age.

You knew that…
Since it can have serious consequences of self-harm or harm to the bedmate and, in many cases, maybe the warning of a neurological disease such as Parkinson’s, it is recommended that a specialist evaluate the patient with it and follow up medically.


Given the importance it has for our physical and psychic health, a good rest is a priority so that we can face our day to day with energy and an optimal mood.

It’s not just about sleeping for a few hours. We must ensure that our sleep is restful. To do this, we must maintain good sleep hygiene.

If you still experience any sleep disturbances, it is always advisable to make a medical consultation to avoid the negative consequences that sleep problems caused in our health.
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