All about the four sleep stages and our sleep cycle
Even though you might not notice it, your body goes through several stages while you’re asleep. During these sleep stages, your body regenerates and you process what you’ve experienced throughout the day. Find out how a healthy sleep cycle is structured and what role the individual sleep stages play in regeneration.
24 July 2024 • 3 min reading time
Understand the different sleep phases and optimise your sleep for more energy and well-being.
A sleep cycle lasts about 90 to 110 minutes. Depending on how long they sleep, most people go through a total of four to six sleep cycles per night. These are organised according to a structure that can be divided into REM and non-REM sleep.
During REM (rapid eye movement) sleep, the sleeping person’s eyes move very quickly; this can be attributed to the intense dreams that occur during this stage.
Comprising the first three of a total of four sleep stages, the non-REM stage includes falling asleep, light sleep and deep sleep. The fourth and final sleep stage is the REM stage, also known as the dream stage. This stage marks the end of every natural sleep cycle, after which most people wake up almost or fully, but quickly fall asleep again before a new cycle begins.
A sleep cycle usually follows this structure: falling asleep à light sleep à deep sleep à REM sleep. Even though falling asleep always occurs at the beginning of a sleep cycle and the REM stage is always at the end, further light and deep sleep stages may follow the first deep sleep stage. Find out below which characteristics are typical of the individual sleep stages.
Falling asleep accounts for 5% to 10% of your sleep, i.e. 5 to 10 minutes per sleep cycle on average. While it often takes a little longer to fall asleep when you first go to bed in the evening, the stages of falling asleep during the night are usually very short. This is why you don’t remember anything the next morning about waking up through the night.
Although we slowly doze off during the stage when we fall asleep, we are easily woken up by external influences such as noises. During this stage, our muscles are not yet fully paralysed; due to sudden muscle twitches, many people have the brief sensation that they’re falling while drifting off to sleep.
At around 50%, light sleep accounts for the lion’s share of a sleep cycle, whereby the last three to four sleep cycles in particular are dominated by light sleep. Our muscles relax during this time, although bursts of activity may still occur. Your body temperature, blood pressure and heart rate drop, your brain activity slows down and you start to regenerate.
For many people, deep sleep only occurs during the first two sleep cycles, which is why it accounts for around 15% to 20% of your sleep. The body regenerates best during this sleep stage. Your blood pressure and heart rate drop sharply so that your body can focus on cell renewal and processing information, memories, etc.
The immune system, metabolism and the production of happiness hormones are in full swing during deep sleep. That’s why this sleep stage has a major impact not only on our physical health, but also on our mental health.
The REM stage accounts for up to 25% of sleep – this equates to just under half an hour in a sleep cycle. Our blood pressure and respiratory rate increase again, but our muscles remain paralysed. This is necessary to prevent us from physically acting out the movements in our dreams, which are very intense at this point. During the REM stage, the release of stress hormones increases again until you’re almost or fully awake.
The sequence and duration of sleep stages, known as sleep architecture, change in healthy people over the course of a lifetime and even over the course of a night. Deep sleep stages decrease and the light sleep stages become longer.
The regenerating effects of deep sleep are also the reason why the first two sleep cycles are particularly important. Babies and children, who have to process a lot of new information during their sleep, therefore spend a significantly longer time in the land of nod – newborns need up to 17 hours of sleep a day. In adulthood, the amount we sleep and, in particular, the duration of the deep sleep stages decrease significantly and the individual sleep cycles become shorter.
Changes to sleep architecture can, however, also indicate the presence of a sleep disorder. This may be the case, for example, if you wake up fully after the REM stage and have difficulties falling asleep. Waking up and not feeling well-rested in the morning can also indicate that the sleep stages are not optimally distributed. In any case, we recommend maintaining healthy sleep hygiene with a regular sleep-wake cycle.
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