Sleep is an essential part of our lives. It not only restores our body, but it is also crucial for our mental health and overall well-being. During a typical night, we go through various sleep stages, collectively known as the sleep cycle. In this blog, we will delve deeper into each stage of the sleep cycle and discover exactly what happens during sleep.
Stage 1: Drowsiness (NREM 1)
The sleep cycle begins with the drowsiness stage, also known as NREM 1. This is a light sleep stage where we transition from wakefulness to sleep. During this stage, you may still be aware of your surroundings and can easily be awakened. Muscle activity slows down, and your eye movements become less frequent. This stage usually only lasts a few minutes.
Stage 2: Light Sleep (NREM 2)
After the drowsiness stage, we enter the second stage of the sleep cycle, known as NREM 2 or light sleep. In this stage, sleep deepens, but you are still easily awakened. During NREM 2, your heart rate and breathing become more regular, and your muscles relax further. This stage accounts for the largest part of your total sleep time and can comprise about half of a normal sleep cycle.
Stage 3: Deep Sleep (NREM 3)
The third stage of the sleep cycle, NREM 3 or deep sleep, is the period of the deepest and most restorative sleep. During this stage, your brain waves are slower, and your muscles are fully relaxed. It can be difficult to wake you during this stage, and if you are awakened, you will likely feel confused or disoriented. Deep sleep is crucial for physical recovery, muscle growth, and a well-functioning immune system.
Stage 4: REM Sleep (Rapid Eye Movement)
The fourth and final stage of the sleep cycle is REM sleep, characterized by rapid eye movements, vivid dreams, and increased brain activity. Although your muscles are temporarily paralyzed during REM sleep, your heart rate and breathing are irregular and accelerated. This stage is essential for processing events, memory, and emotional well-being. It is also the stage where most dreams occur.
Repetition of the sleep cycle
During a typical night, our body goes through multiple cycles of these four sleep stages, with each cycle lasting approximately 90 to 120 minutes. As the night progresses, the duration of REM sleep and light sleep increases, while the time spent in deep sleep decreases. This means that the first half of the night is mainly dominated by deep sleep, while the latter half is more focused on REM sleep and light sleep.
How long does each sleep stage last?
This is how long each stage lasts on average for adults:
- Drowsiness: 1 to 7 minutes in the first sleep cycle, which accounts for 5-10% of total sleep
- Light sleep: 10 to 25 minutes in the first sleep cycle and lengthens with each subsequent cycle, eventually making up between 45-55% of our total sleep
- Deep sleep: 20 to 40 minutes in the first sleep cycle and decreases as the night progresses. Deep sleep accounts for approximately 15-25% of our total sleep.
- REM sleep: only 1 to 5 minutes in the first sleep cycle, but lengthens the more you sleep.
Waking up refreshed
There are different ideas about when the best time to wake up is. During a normal sleep cycle, there is often a brief moment of waking between REM sleep and the next sleep cycle. That moment may be the ideal time to wake up.
Tip: Do you always wake up feeling very tired or disoriented? It might be that your alarm goes off precisely during your deep sleep. You could try experimenting with setting your alarm half an hour earlier or later. Assuming a 90-minute sleep cycle, it is ideal to get up after 7.5 or 9 hours of sleep, when you are coming out of your REM sleep.
Summary
The sleep cycle is an organized process that helps our body and mind recover and renew. During a typical night, we go through different stages, from light sleep to deep sleep and REM sleep, all of which have important functions. A full sleep cycle is essential for good health and well-being, and understanding these stages can help optimize your sleep pattern and wake up refreshed.
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Source: https://www.sciencedirect.com/science/article/abs/pii/0013469485900379
