The stages of sleep explained: how much should you be getting?
The stages of sleep explained: how much should you be getting?
Sleep is part of all our routines, but some manage it better than others. How easy or hard we find it to get an optimal amount of sleep depends on personal factors and potential conditions which can disrupt our sleeping patterns.
To get a sense of how to get better nights of sleep, understanding how sleeping works can help. Sleep essentially has four distinct stages and typically over the course of a night, the body will cycle through these stages four to six times. Each cycle lasts around an hour and a half and we need to experience each stage in order to wake up feeling rested.
The first stage is the lightest stage of non-rapid eye movement (NREM) sleep. It is what occurs just after you nod off and is typically defined by the presence of slow eye movements. The muscle tone throughout the body relaxes and brain wave activity starts to slow down compared to when awake. This drowsy sleep stage can easily be disrupted by loud noises, by being touched or other factors. From time to time, people could also experience abrupt muscle spasms while drifting in and out of this stage.
Have you ever felt suddenly awaken by sharp, unexpected movements of your body or a sensation of falling while trying to sleep? These experiences can happen to a lot of people during Stage 1 of sleeping and such movements are known as sleep starts, hypnic jerks or hypnagogic jerks. These movements could potentially be caused due to a struggle between the part of the brain that promotes waking and the part that promotes sleeping. Other potential contributory factors include stress, exercise before bed, coffee and other stimulants. If sleep starts are happening often to you, it could be a sign of iron deficiency or a side effect of taking certain antidepressants or antihistamines.
The second stage of NREM sleep is like the first stage but ‘deeper’, meaning awakenings or arousals do not occur as easily compared to stage 1.
Slow eye movements stop while brain waves continue to slow with specific bursts of rapid activity mixed in known as sleep spindles. These are intermixed with sleep structures known as K complexes. Essentially, the brain adjusts its activity to protect itself from awakening in preparation for the rest of the sleeping cycle. While all of this is going on, the body also begins to decrease in temperature and the heart rate starts to slow down too.
Stage 3 of NREM sleep is considered the deepest stage of our sleep cycle and it is the most difficult to be woken up from. It is also the most restorative stage of sleep and brain activity in this stage consists of what are known as slow waves and delta waves.
Whereas Stages 1 and 2 are known as the ‘light sleep’ stages, Stage 3 is commonly referred to as ‘deep sleep’. It is during Stage 3 where parasomnias – abnormal or undesirable behaviours during sleep – are the most likely to occur if possible. Examples of parasomnias include sleep talking, sleepwalking and night terrors.
REM – Rapid Eye Movement
After Stage 3 of NREM sleep, the body will shift to a fourth stage known as rapid eye movement (REM) sleep. During this stage, eye movements are rapid, physical movements are more common and brain activity is more active compared to Stage 2 and 3 of NREM sleep.
Compared to these stages, awakening and arousals are more likely to occur but it’s also during this phase where we can have dreams (or, if unfortunate, nightmares!)
How much sleep is the right amount?
Your sleeping patterns and the ideal number of hours you should be spending sleeping depends:
- Newborns (0-4 months old approximately) – Typically up to 16-17 hours of sleep a day. There are no distinct sleep waves for newborns and instead sleep is categorised as ‘active’, ‘quiet’ and ‘indeterminate’. For the majority of time, newborns will be in the active sleep phase which allows for frequent arousals or awakenings, which are necessary for regular periods of feeding.
- Infants (approximately 4 months to 1 year old) – 10-13 hours of sleep in a 24-hour period is typical and standard sleep stage distinction now becomes apparent (though not fully developed yet).
- Toddlers (1 year to 3 years old) – Average sleep time is between 9 and a half and 10 and a half hours in a 24-hour period. Sleeping patterns are now fully developed and children spend around 25% of their sleeping time in Stage 3 deep sleep and almost an equal amount of time in REM.
- Pre-School (3 years to 6 years old) – Average sleep times are similar to toddler at approximately 9 to 10 hours per 24-hour period. While the majority of children will have afternoon naps during their first few years of life, these tend to subside once they reach the age of 3 or 4. Stage 3 sleep remains high in relation to total sleep time.
- School Age (6 years to 12 years old) – Sleep time remains at around 9 to 10 hours per 24-hour period. Stage 3 still covers around 20 to 25% of the total sleep time.
- Adolescent (12 years old and above) – When someone moves into adolescence, their sleep time is typically 9 to 9 and a half hours per 24 hour period. Physiological changes in circadian rhythm occur which leads sleep to commence at a later time then in the past and creates desire to ‘sleep in’ during the morning. As a person progresses well into their adulthood, their circadian rhythm changes again and the total amount of sleep typically required reduces to somewhere between 6 and a half and 8 hours per 24-hour period.
Potential problems with the sleep cycle and treatment
Of course, knowing the typical amount of sleep recommended at different ages is one thing, but actually achieving the right amount is sadly difficult for many. There are numerous sleeping disorders which can disrupt the sleep cycle and cause unwelcome side effects such as drowsiness.
One of the most well-known sleeping conditions is insomnia, which can be experienced by people for a wide range of reasons. There are also potential conditions which can disrupt certain parts of the sleep cycle, such as REM Sleep Behaviour Disorder (RBD), Circadian Rhythm Sleep Disorders and Narcolepsy. There are treatments available for sleeping disorders and some can even be ordered online. For instance, for those looking to treat the neurological condition narcolepsy, you can order Modafinil from iMeds.com.