Sleep is one of the basic biological needs of the body, without which we could not function properly. A sufficiently long night’s rest guarantees well-being and the energy needed to undertake daily tasks. Knowledge of the different phases of sleep can help us improve its quality.
Nowadays, both adults and children sleep much less than they should. According to recommendations, the most sleep is needed by newborns and infants, who sleep between 12 and 17 hours a night. Preschool children only need about 10 hours, and schoolchildren – 9. The number of hours of sleep in teenagers decreases to 8. Adults, on the other hand, can sleep from 6 to 8 hours. Seniors usually need 6-7 hours of sleep per night.
Too little sleep is associated with negative effects on the functioning of the body. As a result of constant fatigue, we lose immunity, and our ability to remember information or speed of reaction is significantly reduced, which can be dangerous when, for example, driving a car. It is worth emphasizing at this point that it is not only the amount of sleep that matters, but also its quality. Knowing the phases of sleep can teach us to control them in such a way that we wake up at the right stage of sleep. Then getting up in the morning will not be difficult, and we will be more sleepy.
Phases of sleep
In a complete sleep cycle, there are two phases of sleep, during which different processes in the body take place. This is related to the different functioning of the body and the different quality of rest in each phase.
The NREM (non-rapid eye movement) phase, known as slow-wave sleep, is characterized by slow eye movement. The REM (Rapid eye movement) phase, also known as paradoxical sleep, is a phase of rapid eye movements.
How exactly does the sleep cycle work? According to studies that took into account bioelectrical brain activity, eye movements and chin muscle tension, adult sleep consists of 2 to 6 cycles. The NREM phase is divided into three stages:
- stage 1 – is the moment of falling asleep, when we lie down with our eyes closed. We may experience feelings of falling and sudden muscle contractions. There are slow eye movements,
- stage 2 – the body prepares for deep sleep, which is manifested by a lowering of the body temperature, a slowed heartbeat and regular breathing,
- stage 3 – deep sleep, a time of intense and best rest for the body. Muscles are relaxed, blood pressure decreases and respiratory rate decreases. Dreams and even sleepwalking may occur during this phase.
The third stage is followed by the REM phase, during which the eyeballs move much faster, blood pressure rises and heart rate and breathing accelerate. In some, paralysis of the limbs occurs. During the REM phase, the mind begins to work more intensely, resulting in more lucid dreams.
The duration of both phases, as well as the entire cycle, is quite an individual matter, depending on many factors. However, it can be approximated that the full cycle is about 90-120 minutes. The first stage of the NREM phase usually lasts 7 minutes, the second – about 20 minutes, and the third usually lasts several tens of minutes. Importantly, with each successive cycle, the deep sleep stage gets shorter and shorter, until it eventually disappears altogether. In contrast, the REM phase of the first cycle lasts no longer than 15 min. Unlike deep sleep, the REM phase lasts longer and longer with each cycle. In the cycle before waking, it is as long as 40 min.
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