In general, people think that getting the recommended amount of sleep each night is enough. They also typically forget about sleep quality and getting restorative sleep which is actually more important than duration.

Namely, the key to getting quality rest is going through the sleep cycle multiple times during the night. And, for those who didn’t know or want to learn more, the sleep cycle is composed of four sleep stages, each playing a huge role in allowing the mind and body to recharge and refresh.

So, let’s have a closer look at everything you need to know about the stages of sleep!

Sleep Stages in a Normal Sleep Cycle

Based on an analysis of brain activity during sleep, researchers have determined four sleep stages: one rapid eye movement (REM) sleep stage and three non-rapid eye movement (NREM) sleep stages.

NREM Sleep Stages

As already noted, a normal sleep cycle features three non-rapid eye movement sleep stages. What’s important to know here is that the higher the stage, the deeper the sleep, i.e., the harder it is to wake up the person.

Stage 1

Also known as N1, stage 1 is basically the period when a person first falls asleep and lasts between one and seven minutes. During this sleep stage, the body isn’t relaxed completely, though activity reduces with instances of brief movements. Plus, as you could guess, it is easy to wake up a person during stage 1. If left undisturbed, a person will soon move into stage 2 and move through further sleep cycles.

Stage 2

During stage 2, called N2, several changes in the body occur such as a drop in temperature, reduced heart rate, slowed breathing, and relaxed muscles. Eye movement stops, brain waves also show a new pattern, and brain activity slows, but with short bursts of activity that help a person to stay asleep regardless of any external stimuli. This stage usually lasts for 10 to 25 minutes during the first sleep cycle and increases with each next cycle.

Stage 3

Stage 3, N3 or deep sleep, is characterized by decreased muscle tone, pulse, and breathing rate. Waking up a person during stage 3 is harder than during stage 2 as the body relaxes even further. Brain activity shows a pattern of delta waves which is why stage 3 is also known as delta sleep or slow-wave sleep. This stage is vital for restorative sleep, the immune system, and other key bodily processes and last for 20 to 40 minutes during the early sleep cycles, and reduce in duration as you continue sleeping.

REM Sleep Stages

Contrary to NREM sleep stages, during rapid eye movement sleep, brain activity increases and the body experiences atonia (temporary muscle paralysis) except the eyes and the muscles responsible for breathing. Indeed, the eyes make rapid movements during this stage although they are closed, which is how the stage got its name.

In addition, rapid eye movement sleep is crucial for cognitive functions like learning, memory, and creativity. It is also characterized by the most vivid dreams due to the uptick in brain activity. And, when it comes to duration, the first REM stage lasts for only a few minutes, whereas the later stages may last for about an hour.

The Bottom Line

In short, all four sleep stages are of great importance as they allow the brain and body to develop and recover. Not getting enough REM and NREM sleep may have a negative effect on thinking, emotions, and physical health. Hence, ensure you get high-quality sleep each night.