The four stages of sleep: What happens during sleep?

Sleep consists of four main phases, which are characterized by different brain wave patterns. These phases are usually repeated 4 to 6 times per night and last about 90 minutes each. The first three phases - falling asleep phase, light sleep phase and deep sleep phase - are collectively referred to as non-REM sleep, while the fourth phase is known as the REM (Rapid Eye Movement) phase.

1. Falling asleep phase (5-10 minutes): This is where the sleep process begins as we fall asleep. During this phase, our body relaxes, our heart rate slows down and our breathing becomes deeper and more regular. However, sleep in this phase is still very superficial and small noises can easily wake us up. Some people also experience the sensation of falling or muscle twitching during this stage, as the brain remains partially active while the muscles relax. The muscle twitching can serve to wake us up.

2. Light sleep phase (40-45 minutes): After the falling asleep phase, we enter the light sleep phase. Here, brain activity is very low and the muscles continue to relax. However, we can still be easily awakened by sounds or light during this phase.

3. Deep sleep phase (10-25 minutes): In the deep sleep phase, our body is completely relaxed, muscles are all but turned off, brain activity is minimal, and breathing is calm and even. It is extremely difficult to wake up in this phase. Deep sleep is crucial for physical and mental recovery and plays a key role in restful and healthy sleep.

4. REM phase (15-25 minutes): REM stands for "rapid eye movement" and refers to the rapid eye movements that occur during this phase. The REM phase is also known as dream sleep, as it is associated with intense dreaming. It is assumed that emotional impressions and information are processed during this phase. During the REM phase, our eyes move quickly and our brain is particularly active.