Nighttime sleep is normally divided into sleep phases. Which ones are there, how long they should last and how important they are for your health – you can read all about that at FITBOOK.
The quality of sleep varies slightly from sleep phase to sleep phase. Researchers distinguish them according to depth, and this is mainly determined by the brain activity during the respective sleep phase. The sleep medicine specialist and general practitioner Dr. medical Michael Feld explained in detail.
Division into three main sleep phases
In the past, people usually spoke of five sleep phases, Feld recalls. In the meantime, a distinction between three main sleep phases is more common.
light sleep phase
The light sleep phase therefore includes the falling asleep phase (also known as “sleep stage one”). In the course of the light sleep phase, our body slowly enters a state of relaxation, our breathing becomes more even and deeper. «The brain is offline at this stage,» Feld tells us.
deep sleep phase
In the deep sleep phase – the name gives it away – we sleep much more soundly. If someone wanted to wake us up now, they would have to try harder than they did during the more superficial phase of light sleep. And we would feel particularly groggy and at times disoriented when “woken from a deep sleep”.
In the deep sleep phase, our skeletal muscles are virtually paralyzed. This time is particularly important for the regeneration of our physical structures – i.e. for our skin and bones, our muscles and the entire immune system.
REM phase
She owes her name to the twitching, rapid eye movements («rightapid eye movement») that for the SEM-phase are typical. Observers can perceive these through the closed eyelids of sleeping people.
The eye movements result from the measurably increased brain activity during the REM phase. In this sleep phase we process information and emotional impressions of the day – not infrequently in very vivid and intense dreams. According to Feld, REM sleep is considered a regeneration phase for the nervous system and the psyche.
«It used to be thought that we only dreamed in REM sleep,» reports Feld. This is one of the reasons why the sleep phase is sometimes called dream sleep. In fact, we also dream in the so-called «non-REM phases», i.e. in the transition from light sleep to deep sleep. But then the dreams are usually less creative and less remembered.
Sleep phases run in cycles
In the course of a night you go through about five cycles in which the individual sleep phases merge into one another in waves. The first half of the night is mainly characterized by light and deep sleep phases. In the second half of the night, light and REM sleep increase.
«We need both deep sleep and REM sleep as the main recovery phase,» emphasizes Dr. Field. However, light sleep is also important.
How long should the individual sleep phases be?
How long the individual sleep phases should ideally last is difficult to say with general validity. After all, the perfect total amount of sleep changes with age.
But one could speak of a suitable percentage distribution. Feld: «A good night’s sleep should consist of 20 percent deep sleep and 20 percent REM sleep, with light sleep accounting for 60 percent.» These are only guidelines that cannot always be achieved. Of course, 15 percent is also fine for the main recovery phases. And if it is even less, then the deficit is usually made up again at another point in time.
Also interesting: sleep paralysis – what is behind the phenomenon and what can you do about it?
Disorders of the sleep phases
In some people, however, the transition between the individual sleep phases is constantly and pathologically disturbed. dr Feld mentions, for example, the finding of narcolepsy – in those affected, the separation between the REM and waking state is disrupted due to a genetic predisposition, which is noticeable with noticeable tiredness and exhaustion during the day.
If you suspect something like this, please have it clarified by a doctor. Various forms of insomnia can be treated. You can help those affected to regain a better quality of life.
Also interesting: Narcoleptics often affected – what is behind the phenomenon of sleep paralysis?
Measurement by polysomnography
dr Feld reports on various apps, sensors to be placed under the mattress and wearables that want to be able to measure the depth of sleep. «But none of this is reasonably possible to this day,» says the doctor. With the help of such DIY equipment, it was at best possible to determine approximate values that result from the heart rate and movements over the course of the night.
For a valid and accurate representation of the depth of sleep, you need «the full wired brain program». In other words: a stay in the sleep laboratory connected to a so-called polysomnograph. According to Dr. Field precisely measure the frequency and amplitude of brain waves, eye activity and other physiological factors.