REM and non-REM sleep: The importance of sleep stages for your health

Why do people sleep?

Modern medicine's understanding of sleep is like a partially assembled puzzle. Experts can identify some pieces and have an idea of ​​what the big picture looks like, but they haven't figured out how it all fits together.

Your body cycles between being awake and asleep every day, with certain processes only taking place when you're asleep. When you fall asleep, your body "shuts down" and most body systems, including the brain, become less active.

Some of the key things that happen while you sleep include:

Energy conservation and storage. During the day, cells in your body use stored resources to continue their work. While you sleep, your body uses less energy. This allows those cells to replenish themselves for the next day.

Self-repair and recovery. By being less active, your body can more easily heal wounds and repair problems that happened while you were awake. Therefore, being sick makes you feel more tired and need more rest.

Brain maintenance. While you sleep, your brain reorganizes and catalogs memories and learned information. It's like a librarian sorting and shelving books at the end of the day. It makes accessing and using what you've learned even easier and more efficient.

What are the stages of sleep?

Sleeping doesn't mean your brain is totally inactive. Although you are less aware of the world around you, you still have a lot of detectable brain activity. Brain activity has predictable patterns. Experts have organized these models into stages. The stages are generally divided into two categories: rapid eye movement (REM) sleep and non-REM (NREM) sleep.

There are three stages of NREM. When you fall asleep, you usually enter NREM stage 1 and then go between NREM stages 2 and 3. After that, you enter REM sleep and start dreaming. After the first REM cycle, you begin a new sleep cycle and return to stage 1 or 2, and the cycle begins again.

One cycle normally lasts about 90 to 120 minutes before another begins. Most people go through four or five cycles a night (assuming they get a full eight hours of sleep).

What is stage 1 NREM sleep?

Stage 1 NREM sleep is the lightest stage of sleep. You enter stage 1 right after you fall asleep. This stage usually lasts only a few minutes, accounting for about 5% of your sleep time. After that, your sleep becomes deeper and you move into stage 2 NREM sleep.

What is stage 2 NREM sleep?

Stage 2 sleep is still light but deeper than stage 1. In this stage, your brain waves slow down and have noticeable pauses between short, powerful bursts of electrical activity. Experts believe that those bursts are your brain organizing memories and information from your waking hours.

Stage 2, NREM sleep accounts for about 45% of your sleep time (the most of any stage). You will go through several rounds of stage 2 NREM sleep, and each one is usually longer than the last. After stage 2, you move deeper into stage 3 NREM sleep or enter REM sleep.

What is stage 3 NREM sleep?

The deepest stage of NREM sleep is stage 3. It accounts for about 25% of total sleep time in adults. But babies and children need more stage 3 sleep, and the older you get, the less you need.

In stage 3, your brain waves are slow but strong. Your body takes advantage of this very deep sleep stage to repair damage and strengthen your immune system. The same bursts of brain activity that occur in stage 2 can also happen in stage 3, and brain waves specific to stage 3 help regulate these bursts.

You need stage 3 NREM sleep to wake up feeling rested. Without enough stage 3 sleep, you feel tired and exhausted even if you've slept for a long time. That's why your body automatically tries to get as much stage 3 sleep as possible into the sleep period as early as possible. After stage 3 NREM sleep, your body moves into stage 2 NREM, which is the guardian of REM sleep.

Because stage 3 NREM sleep is so deep, it is difficult to wake someone from it. If they do wake up, they are likely to have "sleep inertia," a state of confusion, or "mental fog." Sleep inertia lasts about 30 minutes.

What is REM sleep?

Rapid eye movement (REM) sleep is the stage of sleep where most dreams occur. Its name comes from the way your eyes move behind your eyelids while you dream. During REM sleep, your brain activity looks very similar to your brain activity while you are awake.

REM sleep accounts for approximately 25% of total sleep time. The first REM cycle of a sleep period is usually the shortest, about 10 minutes. Each one that follows is longer than the last, up to an hour.

Sleep is a natural process your body uses to rest and repair itself. Although it may seem as simple as closing your eyes and nodding off, sleep is anything but simple, and the correct traversal of sleep cycles, including REM and non-REM phases, is crucial for quality sleep.

Sources:

https://cnchome.ro/blog/somn-profund-cat-dureaza-si-de-ce-este-important

https://my.clevelandclinic.org/health/body/12148-sleep-basics

https://www.healthline.com/health/healthy-sleep/stages-of-sleep#stages-of-sleep