As you get older, it’s normal to notice changes in your sleep. These can include fewer hours of shuteye, waking up more during the night, and finding it harder to drop off. However, despite the general view that older people tend to need less sleep, scientific evidence suggests that this change isn’t actually a question of needing less rest, but of a reduced ability to fall into a deep, continuous sleep.
Older brains still need to rest, but they find it harder and do it more superficially. It’s as if the “off switch” that keeps us asleep works less effectively as time goes on.
Lighter sleep and ageing
One of the main reasons we get worse sleep as we age is the loss of stability in the system that regulates sleep and wakefulness.
In the young brain, this system functions like a firm switch: it is either awake or asleep. But as we get older, some neurons that promote and maintain sleep are lost, while others that sustain wakefulness also get weaker. As a result, the brain shifts states more easily, leading to lighter and more fragmented sleep.
Our biological clocks also change with age. The group of neurons that coordinates the entire body’s circadian rhythms (known as the suprachiasmatic nucleus) continues to function, but its “day” becomes shorter and starts earlier, and its signal becomes less intense.
This partly explains why older people tend to fall asleep and wake up earlier. It also explains why their night-time sleep is more sensitive to external stimuli, and why they can experience more drowsiness during the day. Put simply, the brain receives a less clear signal about when to sleep and when to stay awake.
Another significant change is in our “sleep pressure”. This urge builds up throughout the day and causes us to sleep at night, and depends on a substance known as adenosine. As we age, the brain continues to accumulate fatigue but responds less effectively to this signal. Although the need for sleep remains, it becomes more difficult to translate the signal into deep, uninterrupted sleep.
Deep sleep, which is essential for brain recovery, is also directly affected by structural changes in the brain. This phase of sleep occurs primarily in the frontal regions, which lose thickness and connections as we age. As a result, the slow brainwaves that characterise deep sleep become weaker and less frequent – especially at the start of the night.
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During sleep, the brain also sends out brief signals that help consolidate memories from the day. As we age, these signals diminish and become less synchronised with deep sleep. This contributes to a decline in learning and memory efficiency, even in healthy older people.
Finally, ageing affects the connections that enable different regions of the brain to work in sync during the night. Although the neurons that generate sleep are still present, their signals are transmitted less effectively. The result is less deep, more fragmented, and less restorative sleep.
It is important to note that lighter sleep is considered part of the brain’s natural ageing process in healthy older adults. These changes do not necessarily lead to cognitive problems.
Lifestyle factors
In addition to these biological changes, other factors can have a decisive influence on sleep in older people, and often interact with neurobiological mechanisms. For instance, the loss of daily routine – such as regular working hours, structured physical activity and consistent exposure to natural light – weakens the external cues that help synchronise the biological clock, exacerbating sleep fragmentation.
At this stage of life, sleep disorders such as insomnia and obstructive sleep apnoea are more common. At the same time, a greater burden of chronic conditions – persistent pain, cardiovascular or respiratory diseases – and mood disorders leads to additional night-time awakenings and breaks up sleep.
While essential, frequent use of medicines can also disrupt sleep patterns. These range from sleep aids and anxiolytics that affect deep sleep, to antidepressants, beta-blockers and diuretics that interfere with the onset, stability or continuity of sleep.
Taken together, these factors act as modulators. While they do not in themselves cause sleep ageing, they can exacerbate it, and make it clinically significant when they occur in a brain that is already more vulnerable.
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What is “normal” sleep ageing?
In recent years, there has been a growing body of evidence regarding the harmful effects of sleep deprivation and sleep disorders on brain health. Poor sleep is not only associated with poorer cognitive performance in the short term, but also with a higher risk of cognitive decline and dementia in the long term.
This growing interest has placed a spotlight on sleep in old age, a stage of life where sleep patterns almost universally change. However, one of the greatest challenges is to draw a clear line between changes in sleep that are part of normal ageing – meaning they don’t entail any negative physical or mental consequences – and those that may constitute an early, subclinical symptom of neurodegenerative processes.
As they age, a person might begin to notice a deterioration in their sleep patterns (waking up during the night, more superficial sleep, and so on). But there are no biomarkers that can determine whether these are normal changes to be expected with age, or whether they are in fact a manifestation of neurodegenerative disease.
Although it’s normal for sleep to become lighter with age, some changes go beyond what is to be expected and may indicate unhealthy brain ageing. One of the main warning signs is marked and progressive sleep fragmentation, with multiple prolonged night-time awakenings and a persistent feeling of non-restorative sleep, even when the total time spent in bed is enough. Unlike normal ageing, in these cases sleep loses its stability and continuity.
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Another key sign is the rapid onset or worsening of excessive daytime sleepiness, particularly when it interferes with daily activities or is disproportionate to the amount of sleep obtained. This would suggest that a person’s sleep has lost its restorative function.
When should you worry?
From a neurocognitive perspective, the coexistence of sleep disturbances with subtle cognitive changes – such as recent difficulties with memory, attention or learning, even if these do not yet meet the criteria for cognitive impairment – is particularly concerning. Recent research suggests that this combination may reflect early-stage neurodegenerative processes.
Changes in quality of sleep, rather than simply a reduction in sleep duration, are also considered warning signs. This can mean the almost complete disappearance of deep sleep, a marked reduction in REM sleep, or a progressive reversal of the sleep-wake cycle, with increased night-time activity and daytime sleepiness. These patterns are not typical of healthy ageing.
Other warning signs are a growing dependence on medical sleeping aids or sedatives to sleep, as well as treatments that previously worked becoming suddenly ineffective. In these cases, the problem is usually not just insomnia, but an underlying disturbance of the brain’s sleep mechanisms.
These signs alone are not sufficient to diagnose a neurodegenerative disease, but they do show why we need to assess sleep as a potential early risk marker, especially when the changes are recent, progressive and associated with cognitive impairments.
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