How long is a sleep cycle and what happens in each phase?

What is the sleep cycle?

You probably know the feeling of "dozing off" before you fall asleep. Or the scattered feeling when someone wakes you up while you were immersed in a deep sleep. This shows that sleep is not always the same. During sleep, you go through four different sleep stages. All the stages together are called a sleep cycle. You go through this cycle about four to six times a night.

All sleep cycles vary in length (often the first cycle is the shortest) and are influenced by many factors such as age, sleep patterns, alcohol, caffeine, physical pain and stress. On average, a sleep cycle lasts 90 to 120 minutes.

What sleep stages does a sleep cycle consist of?

A sleep cycle consists of four sleep stages: slumber stage, light sleep, deep sleep and REM sleep. You can tell which sleep stage you are in by your brain activity at that time.

NREM sleep

The first three sleep stages fall under NREM (Non Rapid Eye Movement) sleep.

Slumber stage (stage 1)

The slumber stage is the transition between being awake and asleep. Your brain activity decreases, which causes you to fall asleep. At this time, your consciousness is still active and you can still respond when someone calls your name.

Light sleep (phase 2)

During the second phase, your body temperature goes down and your breathing and heart rate slow down. You are relaxed but can still be easily awakened. During this stage, your brain activity is lower and your eyes stop moving.

The second phase lasts about 10 to 25 minutes. If you wake up during this phase, you have a relaxed feeling, but you are not yet fully rested. This is similar to waking up after a nap. It is therefore also wise not to nap for more than 30 minutes (you feel more awake but have not yet sunk into a deep sleep).

Deep sleep (stage 3)

During deep sleep your body is completely relaxed and has the opportunity to recover. Deep sleep is therefore essential if you want to wake up rested. It strengthens your immune system and supports other important processes in your body.

This phase is also called delta sleep or wave sleep. This is because during this phase, waves form in our brain that form a delta pattern. These slow waves create relaxation, slow breathing and energy for the new day.

Deep sleep is most common at the beginning of the night and a phase lasts about 20 to 40 minutes.

REM sleep (phase 4)

REM (Rapid Eye Movement) sleep is also called dream sleep and is the last part of the sleep cycle. During this stage, brain activity is high and you can see your eyes moving rapidly (even though they are closed). This is because your brain is processing the experiences of the past day.

Because your brain is active, you may have vivid dreams during REM sleep. Your muscles are completely paralyzed during this phase. Although this may sound scary, this happens to protect yourself. If this protective mechanism were not there, you could jump out of bed to chase your dreams and hurt yourself in the process.

Learn why REM sleep is important and how to improve the quality of your REM sleep.

Why are sleep stages important

Sleep allows us to function well in everyday life. A sleep deficit or lack of deep sleep or REM sleep, can lead to negative effects on your physical and mental health. Not only do you feel tired during the day, you are less alert, experience mood swings and are more likely to gain weight.

Do you recognize the above symptoms? Learn how much sleep you need as an adult and what to do if you're not getting enough sleep.

How can I ensure a healthy sleep cycle?

Do you regularly wake up at night? Are you easily irritable? Or are you often tired during the day and this causes you to lack focus? These are all signs that the quality of your sleep cycle is not optimal. How do you ensure a healthy sleep cycle?

• Make sure your bedroom is cool and dark
• Go to sleep at set times
• Avoid technology an hour before you go to sleep to allow your brain to unwind
• Avoid alcohol and caffeine
• Exercise during the day

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