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ZZZZ: A Primer on Sleep Stages

Sleep is a vital part of the recovery process post-concussion. In the past medical experts advised that a person who has sustained a concussion, should stay awake as long as possible – the theory here being that sleeping with a concussion could cause you to fall into a coma or worse, die. Thankfully, medical consensus now is that it is safe for a person to sleep if they have a concussion, but best practice is to have somebody stay with them to monitor their symptoms, especially in cases of severe concussion.

Sleep, the Brain Healer

Did you know that there are several stages of sleep? You’ve probably heard of ‘deep sleep’ and ‘light sleep’, but can you name the other stages – and do you know their purposes?

Sleep is broken up into four distinct stages, each with their own benefits, and while asleep we cycle though each stage [1]. Over the course of a typical night, a person goes through four to six sleep cycles [2]. Quality sleep is achieved by successfully moving from stage to stage and cycle to cycle each night. If you are woken, you may have to start right from the beginning!

Sleep Stages

Light Sleep

· N1 (NREM 1)

· N2 (NREM 2)

Deep Sleep

· N3 (NREM 3)

REM Sleep


REM = Rapid Eye Movement

NREM = Non REM Sleep

Stage N1 (NREM 1)

The first stage of sleep is stage N1, where we transition from being awake to falling asleep, and usually lasts 1 – 7 minutes in duration. In stage N1, your brain waves, heartbeat, eye movement and breathing all slow down as you relax, and fall into sleep.

It is easy for someone to wake up in this stage, but if left undisturbed, a transition to Stage N2 can occur quickly. Throughout the night a person may not spend very long in this stage before moving to into the next stages.

Stage N2 (NREM 2)

During this stage, the body enters sleep and a more relaxed state. Following on from stage N1, there is a slowing of your heart rate and breathing rate, as well as a relaxation of your muscles and a drop in internal body temperature.

Eye movement stops in this stage, and brain activity slows, but there are short bursts of rapid, rhythmic brain activity called sleep spindles. Sleep spindles are important for memory consolidation, and ensuring you are not woken by external disturbances [3].

Throughout the night, you should spend about half your sleep time in stage N2. At the beginning of the night, stage N2 can last from 10 – 25 minutes, but this then can increase in duration as the night progresses.

Stage N3 (NREM 3)

Stage N3, or the deep sleep stage is particularly important as it’s in this stage that your body heals and repairs, even the brain itself. It’s harder to wake someone in this stage on account of the relaxed state of the physiological system. The stage typically lasts from 20 – 40 minutes, but more time in spent in it at the beginning of the night, with more time being spend in REM sleep later as the night progresses.

Alongside healing and restoration, this stage also can also positively contribute to insightful thinking, creativity and memory [4, 5].

REM Sleep

It’s in this stage that your brain activity increases, almost to the same levels as when you’re awake, as exemplified by the name of the stage ‘Rapid Eye Movement’, where your eyes literally move rapidly behind your eye lids.

REM sleep has a range of benefits, including improvement in memory, learning and creativity [6]. REM sleep is also well known as the dream stage, and the vivid nature of these dreams can be attributed to the increase in brain activity. You can dream in any stage, but it’s most common and less vivid in other stages.

REM sleep doesn’t usually occur until after you’ve been asleep for approximately 90 minutes, and increases in duration as the night progresses and you re-enter this stage. Broadly, as the night progresses this stage can range from 10 – 60 minutes.

Top Tips for Improved Sleep

Sleep Hygiene refers to ways in which you can set yourself up to sleep better, and it’s another big topic in itself - Although, it can be nicely summarised by the 10-3-2-1-0 rule [7].

10 – Stop drinking caffeine 10 hours before bed.

3 – Limit food and alcohol for 3 hours before bed.

2 – Stop working at least 2 hours before bed.

1 – Avoid screen time in the hour before bed.

0 – The number of times you should hit the snooze button on your alarm.


Daniel Glassbrook, PhD

Daniel is a sports scientist and researcher, currently working as the first team sports scientist for the Newcastle Falcons Rugby Club, and a postdoctoral researcher in sports related concussion at Durham University.


1. Suni, E. Stages of Sleep. 2023; Available from:

2. Patel, A.K., V. Reddy, and J.F. Araujo, Physiology, sleep stages. 2022, StatPearls Publishing.

3. Schönauer, M. and D. Pöhlchen, Sleep spindles. Current Biology, 2018. 28(19): p. R1129-R1130.

4. Yordanova, J., et al., Differential associations of early-and late-night sleep with functional brain states promoting insight to abstract task regularity. PLoS One, 2010. 5(2): p. e9442.

5. Drago, V., et al., Cyclic alternating pattern in sleep and its relationship to creativity. Sleep medicine, 2011. 12(4): p. 361-366.

6. Peever, J. and P.M. Fuller, The biology of REM sleep. Current biology, 2017. 27(22): p. R1237-R1248.

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