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The sleep cycle

At night time we experience different levels of sleep and we sleep in cycles.  The stages of a sleep cycle are:

Non-Rapid Eye Movement (Non-REM)

Stage 1 – a very light sleep, where you will be easily woken.  If you have ever tried tip toeing out of your child’s bedroom and they’ve woken this is why – they were in a very light sleep.

Stage 2 – still quite a light sleep but the body is preparing for the deep sleep that is about to come. Your child will be more relaxed now and if you are trying to sneak out of their bedroom this is a good time to make your exit!

Stage 3 – this is a very deep sleep.  The body needs this sleep so that repair can take place.  It will be difficult to wake your child when they are in this stage.


Rapid Eye Movement (REM stage)

Sleep then moves into a phase of Rapid Eye Movement (REM stage). REM stage sleep is when dreams occur.  It is vital for mental and emotional development.  Brains can become very active during REM sleep yet out bodies are relaxed.


Figure 1: Non-Rapid Eye Movement (Non-REM) and Rapid Eye Movement (REM) stages

Sleep toolkit Figure 1


Each cycle usually lasts for around 90 minutes and is slightly shorter for infants (45-60 mins)

The sleep cycles occur throughout the night.  We are usually in deep sleep towards the beginning of the night and lighter sleep in the early hours of the morning.

After each cycle we come to a point of partial waking (the red bars on figure 2).  If everything is as it was when we fell asleep we may well just roll over and carry on sleeping as in figure 2:


Figure 2

Sleep toolkit Figure 2

Source: Sleep Training, Southampton


If anything has changed however……that’s when we wake up, as described in figure 3:


Figure 3

Sleep toolkit figure 3

Source: Sleep Training, Southampton


It is important for sleep conditions to remain the same throughout the night as connecting sleep cycles is about waking and feeling safe and secure enough to drift back off to sleep. This often happens when children are developmentally ready and have a secure environment.  Infants often need parental input to fall asleep and connect their sleep cycles as they are not developmentally ready to ‘self soothe’.


Circadian Rhythm, often called the ‘body clock’

We all have a sleep-wake cycle known as the circadian rhythm or body clock which is regulated by light and dark.  The rhythms take time to develop in new-borns and it is very normal for infants and young children to wake regularly during the night. By about 6 months most babies have a regular sleep-wake cycle.  Putting children to bed at the same time each night and waking them up at the same time each morning, even at weekends, will help to enable a regular sleep-wake cycle.  When the hour changes from winter time to summer time some children’s sleep-wake cycle goes off track.  A child’s sleep-wake cycle can be reset by bringing bedtime forward by 15 minutes every three nights until the desired time is reached.



Melatonin is a hormone that occurs naturally in our body when it gets dark. It helps us sleep.  It is a good idea to put your child to bed in a dark environment and dim lights in the run up to bedtime.

Melatonin production is negatively affected by screen activity, like watching a television/iPad or playing computer games.  The light from the screen stops melatonin being produced. Avoiding these activities in the hour (or more) leading up to bedtime is a good idea to help the sleep cycle.  Some children and those with autistic spectrum disorder may produce less melatonin.


Source: Sleep Health Foundation 


How much sleep is needed? Sleep duration

Sleep needs change as children get older and every human requires a different amount of sleep throughout their life.  However, there is a recommended number of hours to aim for:


Figure 4

Sleep toolkit figure 5

Research suggests that, in Western societies, many adults and some children and young people are under-sleeping by roughly one hour per night due to lifestyle changes.  When accumulated over one week this adds up to a sleep deficit of about one full night.

Source: Royal Society for Public Health (2016) Waking up to the Benefits of Sleep, University of Oxford


Sleep routines, sometimes called ‘sleep hygiene’

Daytime activities

What happens in the day can effect sleep: exercise improves sleep onset (how long it takes to fall asleep). Diet during the day can affect sleep. Caffeine blocks the sleep-wake regulation.

Sleep Environment

The sleep environment needs to be safe, a comfortable temperature, with space to lie down, low level of noise, low light or darkness and a lack of distractions.

Bedtime routines

Routines can teach children to associate a sequence of events e.g. upstairs, bath, brush teeth, PJs, to bed, story time etc. with bedtime and sleep.