Our sleep needs and the sleep stages we have all change throughout our life span, especially in childhood. As adults, our sleep requirements are relatively consistent, however, they do reduce a little in older age.
In this blog post, Dr Lindsay Browning shares more information about the connection between age and sleep, including how much sleep we need, changing sleep patterns and natural sleep times. Understanding this can be really helpful as we pass through major milestones in age.
How much sleep do we need?
As can be seen in the graph, the amount of sleep required continues to decrease throughout a life time.
From 0-3 months, babies can need as much as 17 hours sleep. Once adulthood is reached, at approximately 18 years olds, then the recommended average of 7-9 hours of sleep remains consistent throughout our lives, until around retirement. This is when sleep needs actually decrease a little further.
How does our sleep change across our lifetime?
When we fall asleep, our brains don’t switch off. We have different kinds of sleep which provide different benefits. Generally speaking, these different kinds of sleep (or sleep stages) are called light sleep, deep sleep and dreaming sleep (also known as REM sleep). We tend to sleep in sleep cycles where we cycle through these different sleep stages in regular intervals through the night.
These sleep stages, and the proportions of each, develop and change through our lifespan, as well as the total amount of sleep that we need.
In an adult, each sleep cycle is around 90 to 110 minutes long and consists of light sleep followed by deep sleep and then ending with REM sleep. The sleep cycle would then start again.
Babies and sleep
Newborn babies fall asleep directly into a dream-like sleep (not quite REM sleep, but similar) whereas older children and adults have REM sleep at the end of each sleep cycle rather than at the start. Newborn babies have sleep cycles that are around 50 minutes long. Also, newborns do not have a clear day and night rhythm for sleep. They produce growth hormones during the day and night equally.
By the time babies reach around two months old, they have started to develop a circadian pattern to their sleep with them more likely to sleep at night and more likely to be awake during the day. Also, at this point, they start to fall asleep into a sleep resembling light and deep sleep, rather than going directly into a dream-like sleep (which more resembles the pattern of sleep cycles we see for the rest of our life). Finally, they also start to produce growth hormone more prominently at night, especially during their deeper sleep, and by the time they are 6-9 months old their sleep cycles move towards a more standard 90 minutes.
Children and sleep
For children, their deep sleep is deeper than that we have as an adult. Younger children tend to have even deeper sleep than older children, which is characterised by greater amplitude of delta waves (or delta power) seen in brain EEG. This deeper sleep means that children are harder to wake than adults.
Growth hormone is produced during deep sleep and since babies and younger children are growing at a faster rate it makes sense that their sleep would be deeper, than older children and adults. During adolescence, the delta power of deep sleep decreases significantly, and it may drop by 50% between 10 and 20 years old. The decline generally occurs earlier in girls than boys, and correlates with the degree of sexual maturation.
Young adults and sleep
In young adults, they spend approximately 25% of the night in REM sleep, 20% of the night in deep sleep and 55% of the night in light sleep. Compared to children, young adults need less loud stimuli to wake them from deep sleep. Young adults also report few awakenings during the night.
Adults and sleep
As people age (until 65 years old) total sleep time remains relatively stable but slow wave sleep declines slowly throughout this period. With an increase in age comes a greater number and awareness of awakenings during the night.
In adults over 65, the total amount of sleep required decreases a little – learn more in an article I contributed to for Saga.com. Also, deep sleep (delta power) appears to decrease, and in some people they have no deep sleep whatsoever. This is especially true in men compared to women. This decrease in deep sleep has been linked to an increased risk of dementia, specifically a build-up of amyloid plaques, which have been linked to Alzheimer’s disease.
How does ‘when we sleep’ change?
The timing of when we sleep changes as we age.
As already mentioned, newborns don’t have a day-night sleeping pattern, but by the time they are two months old they have started to develop a circadian pattern to their sleep sleeping more at night than during the day. Children, until adolescence, have a tendency to fall asleep during the mid-evening and wake up early (much to parents’ dismay!). However, once children hit adolescence their circadian rhythm moves them to want to go to sleep later and wake up later. This is often perceived as teenagers being lazy because they are hard to wake in the morning, but this is a biological fact about their changing circadian rhythm. People have suggested that this change in when teenagers sleep could be so that teens would be awake late in the night, while the adults were sleeping, allowing them to have some space to develop their personalities without their parents around.
Once teenagers hit adulthood, their circadian rhythm shifts back towards a typical adult pattern of slightly earlier bedtime and wake time. This circadian pattern remains fairly stable until old age when it can shift earlier again to resemble a young child’s sleeping time of early evening sleep and very early morning awakening. This is why many elderly people find themselves falling asleep very early in the evening and waking much too early in the morning.
Are you getting the recommended amount of sleep for your age?
Consider if you and, also, your children are getting enough sleep, in line with the discussion above. If you are struggling with falling asleep, finding yourself waking early or consistently waking in the night, then you may need some support.
From attending a workshop to booking an initial consultation, I am here to help with any trouble sleeping.