A tour of our night brain: the stages of sleep
by Floris Biesemans on Feb 08, 2023
Every night you go to sleep and every morning you wake up. But what actually happens when we are sleeping? Whether our nights last 4 hours or 10 hours, each time we go through some defined phases. The sleep-in phase, a phase of wakefulness, NREM, REM and deep sleep. Maybe you already know about these sleep stages, or maybe you've never heard of them? No problem, this blog will discuss each phase for you separately.
The falling asleep phase
The falling asleep or nap phase is the phase between wakefulness and sleep, where we become increasingly sleepy and finally fall asleep. This phase lasts about 5-10 minutes and during this phase the activity of our brain changes. Our eyes move slower and our muscles relax, making us increasingly sleepy.
During the falling asleep phase, we are still able to stay awake, but it becomes increasingly difficult to stay alert as we get closer to sleep.
The light sleep phase
Light sleep, NREM (Non Rapid Eye Movement) Stage 1-2, is the stage between wakefulness and deep sleep and the body and brain are not yet fully asleep. In this stage, it is easy to wake up to sounds or other stimuli and sleep is even more superficial. During this phase, eye movements can still be observed and the brain is still active. It is normal to wake up several times during the night during light sleep, but it is not necessary to wake up to continue deep sleep. Light sleep generally lasts about 60 minutes and is important for body and brain health.
The deep sleep phase
Deep sleep (NREM stage 3) is a stage is characterized by regular breathing, declining heart rate and relaxed muscles. During deep sleep, we are not awake and our brain is actively processing information and repairing the body. It takes about 20 minutes for us to enter this phase. Also, this phase lasts an average of 20 minutes. When we wake up during this phase, we feel confused and it sometimes takes us a while to realize where we are. Deep sleep is important for our physical rest and recovery. At the end of this blog, we will discuss why adequate (deep) sleep is hugely important.
The REM sleep phase
REM (Rapid Eye Movement) sleep is an important part of the sleep cycle and usually takes place about 90 minutes after falling asleep. This phase lasts about 20-30 minutes and is characterized by rapid eye movements, high brain activity and increased heart rate and breathing.
During REM sleep, our muscles are paralyzed and we are not consciously awake, but our brain is actively dreaming and processing emotions, thoughts and experiences. REM sleep is important for our emotional and cognitive health and for our ability to learn and remember.
It takes about 60-90 minutes to enter REM sleep, depending on individual sleep cycle and sleep habits. It is normal to be in REM sleep about 4-5 times a night, and the duration of this phase increases as the night progresses.
The average sleep schedule
An average nightly sleep schedule is as follows:
- Falling asleep phase (0-30 minutes): The body relaxes and the heart rate and breathing slow down.
- Light sleep phase (30 minutes - 1.5 hours): The body remains relaxed and muscles are still unaffected by movement.
- Deep sleep phase (1.5 - 2 hours): The body is most relaxed and the muscles are not affected by movements.
- REM sleep phase (2 hours - end of the night): This phase is characterized by rapid eye movements and dream-like awareness.
This schedule will repeat throughout the night, with increasingly longer REM sleep phases. So basically, you go through the same cycle several times during a night, with the difference being that as the night progresses, you enter both the deep sleep phase for less time and less often, and the REM sleep phase for longer.
Is a lack of sleep bad?
With too little sleep, the body can develop serious health problems, including:
- Decreased concentration and reaction time
- Memory problems
- Humor and emotional instability
- Decreased resistance to illness
- Increased stress and blood pressure levels
Each stage of sleep is important for the health and well-being of the body, but the deep sleep stage is specifically important for the growth and repair of muscles and tissues.
The exact number of hours of deep sleep you need depends on many factors, including age, activity level and general health. On average, an adult needs about 1 to 2 hours of deep sleep per night.
Do you have some sleepproblems? Read our blog - Sleep problems - what is it and how to get rid of it?