What are the different types of sleep? Non-REM and REM sleep stages defined, plus the sleep cycle explained

Everybody experiences both light and deep sleep every night
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Sleep is crucial for maintaining and improving physical and mental health. When we settle down and fall asleep each night, our body goes through different stages of sleep. There are two main types of sleep: non-REM (NREM) sleep, which is deeper sleep, and rapid eye movement (REM) sleep, which is lighter sleep. We all experience these two types differently, depending on various lifestyle factors including age and also health factors such as stress levels. 

This March, as it’s National Bed Month, World Sleep Day and Sleep Awareness Week, NationalWorld has spoken to several sleep experts to explain all about non-REM and REM sleep. Read on to find out more about the different types of sleep, what a typical sleep cycle looks like and the benefits of each type of sleep. For even more information about all things sleep-related, you can check out our dedicated sleep page, including unusual tips to help you sleep better, the recommended amount of sleep for people of all ages and common dreams explained.

How long does each stage of sleep last?

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There are not only two types of sleep, but also different stages of each type of sleep. Specialist sleep psychotherapist Heather Darwall-Smith describes them below:

The first stage of sleep that we enter when we fall asleep is Non-REM (NREM) Sleep. It is divided into three stages:

  • Stage 1: This is the lightest stage of sleep and usually lasts only a few minutes. It's quite wakeful but you are technically under the sleep barrier.

  • Stage 2: This stage lasts for about 20-30 minutes.

  • Stage 3: This is the deepest stage of sleep, also known as slow-wave sleep, and is important for rest and recovery. During this stage, your brain waves slow down and it is difficult to wake up.

Experts explain the two different types of sleep, why we need both and the typical sleep cycle.Experts explain the two different types of sleep, why we need both and the typical sleep cycle.
Experts explain the two different types of sleep, why we need both and the typical sleep cycle.

The second stage of sleep occurs after the NREM stages, Rapid Eye Movement (REM) Sleep, and is characterised by rapid eye movements, increased brain activity, and vivid dreams. REM sleep usually occurs about 90 minutes after falling asleep and recurs several times throughout the night, getting longer with each cycle. During REM sleep, the body is paralysed to prevent acting out dreams, and breathing and heart rate may become irregular. The brain is active and uses this time to consolidate memories, process emotions, and repair the body.

A person's typical sleep cycle explained.A person's typical sleep cycle explained.
A person's typical sleep cycle explained.

What happens to the body during the stages of sleep?

There are various changes in the body during the different stages of sleep. Emma Roberts, a Level six sleep coach with over 15 years experience, explains them below.

NREM 1 Sleep 

  • Your brain slows down

  • Your heartbeat, your eye movements, and your breathing slow with it

  • Your body relaxes, and your muscles may twitch

NREM 2 Sleep

  • You become less aware of your surroundings

  • Your body temperature drops

  • Your eye movements stop

  • Your breathing and heart rate become more regular

Emma Roberts, a Level six sleep coach.Emma Roberts, a Level six sleep coach.
Emma Roberts, a Level six sleep coach.


  • Your muscles are relaxed

  • Your blood pressure drops, and breathing slows

REM Sleep

  • Your brain is active

  • Your body is relaxed and in a form of paralysis

  • Your breathing is fast and irregular

  • Your eyes move rapidly

  • You dream

What is a typical sleep cycle?

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The sleep cycle is the pattern in which NREM and REM sleep alternate throughout the night. It typically lasts 90 to 110 minutes and repeats four to six times per night. The first sleep cycles of the night contain more deep sleep, while the later cycles contain more REM sleep. A typical sleep cycle, according to Darwall-Smith, looks like this:

  • Stage 1 NREM

  • Stage 2 NREM

  • Stage 3 NREM (slow-wave sleep)

  • Stage 2 NREM

  • REM sleep

Specialist sleep psychotherapist Heather Darwall-Smith.Specialist sleep psychotherapist Heather Darwall-Smith.
Specialist sleep psychotherapist Heather Darwall-Smith.

What are the advantages and disadvantages of light and deep sleep?

We all go through light and deep sleep each night, even if we’re not always aware of it, and each type can have various impacts on us. 

Darwall-Smith said: “Something that is always interesting is someone's perception of their sleep. The amount of light sleep someone gets each night can vary depending on age, lifestyle factors, and individual differences. However, on average, light sleep accounts for around 50% of the total sleep time in healthy adults. During light sleep, people can sometimes feel like they are awake but are actually asleep. This can happen because they are in a light stage of sleep, and external stimuli, such as noise or movement, can easily wake them up. This is particularly true during the early part of the night when more light sleep occurs.

“In addition, people can sometimes experience episodes of sleep paralysis where they have a temporary inability to move or speak. While light sleep is necessary for overall sleep quality and helps prepare the brain for deeper stages of sleep, disruptions to this stage of sleep can affect overall sleep quality and lead to daytime sleepiness and other health problems.”

Solution focused psychotherapist Gin Lalli.Solution focused psychotherapist Gin Lalli.
Solution focused psychotherapist Gin Lalli.
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Gin Lalli, solution focused psychotherapist, said: “Deep sleep is good for you physically - your muscles, organs, skin, hair and so on. Lots of cell repair goes on during deep sleep and you need plenty of this."

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