Dreaming of a world without dementia: all you need to know about sleep and dementia


By Emma Taylor | Wednesday 22 December 2021

Although getting a good night’s sleep can help us feel sharper and healthier, current research reveals that the links between sleep and dementia are complex. Less understood than other risk factors, we’re not yet certain whether dementia causes poor sleep, or whether poor sleep may contribute to the development of dementia.

Why is sleep important?

By measuring changes in brain signals, we can tell that our brains work quite differently when we’re asleep. Evidence suggests these different functions may help protect us against diseases that cause dementia.

A good night’s sleep increases the functioning of the brain’s glymphatic system. This is like the brain’s drainage system, flushing waste molecules, including amyloid, a toxic protein involved in Alzheimer’s disease, out of the brain. During sleep, it is estimated to work up to 60% more efficiently.

So sleep helps the brain to clear away proteins that in some people can build up over time to cause dementia. To learn more about the glymphatic system and amyloid clearance read our blog here.

Building on this research, we’re funding a project at the University of Camerino in Italy which will investigate whether boosting the quality and duration of sleep can slow the build-up of another key protein involved in the development of Alzheimer’s, called tau.



Sleep and dementia risk

There is a growing body of evidence that links poor sleep with an increased risk of developing dementia.

In one recent study, a team of researchers in London and Paris found that sleeping for less than 6 hours a night between the ages of 50 to 70 was associated with an increased risk of dementia of up to 30% compared to people of the same age who slept for seven hours or more. This study looked at people who had displayed poor sleeping patterns for years, not just days or weeks.

But the links between sleep and dementia are difficult to unravel. We know that around 70% of people diagnosed with dementia have a history of disrupted sleep. These disruptions can take many forms and scientists are now trying to unpick whether they are a very early symptom of, or are playing a role in causing, diseases like Alzheimer’s.

To make things even more complicated, many conditions that can increase our likelihood of developing dementia are also associated with poor sleep, such as:

  • high blood pressure
  • sleep apnoea
  • Type 2 diabetes
  • mental health conditions like depression and anxiety
  • heart disease.

This can make it harder for researchers to tell whether changes in sleep patterns are linked to dementia or a pre-existing condition. Having one of these conditions by no means guarantees that you will experience either poor sleep or develop dementia, but they are associated with an increased risk of both.


Brain health basics tile


Poor sleep as a symptom of dementia

Some researchers have suggested that disrupted sleep is a very early symptom of dementia, that affects people years before noticeable problems with memory and thinking develop. If this is proven to be the case, then poor sleep could be used as a red flag for early diagnosis of dementia. We know that the diseases that cause dementia start to develop decades before the more noticeable symptoms start. So the earlier we diagnose these diseases, the better chance we have of intervening, treating them and potentially slowing their progression.

Poor sleep can affect our memory. So if someone with dementia has trouble sleeping, it can be hard to assess the extent to which their memory problems are directly linked to their condition or their poor sleep. Strategies to improve sleep quality may help some people with dementia to maintain better memory and thinking skills.

In the later stages of dementia, it is common for people to sleep more during the day. This is because as diseases like Alzheimer’s get worse, simple tasks such as eating or talking, can become very tiring for the body and brain. Additionally, some medications taken for the symptoms of dementia, including antidepressants and antipsychotics, can contribute to tiredness.

So, how much sleep should you get?

Overall, evidence so far points to having at least seven hours a night to help boost our brain health. However, the occasional late night won’t do much harm as research suggests long lasting negative effects are only seen after prolonged periods of poor sleep.

To find out more about the relationship between sleep and dementia, watch our Lab Notes session led by researchers in the field or contact the Alzheimer’s Research UK Infoline team on 0300 111 5111 or infoline@alzheimersresearchuk.org.

If you have any concerns about your own sleep, the best thing to do is to contact your GP who can assess your situation and give you advice.

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About the author

Emma Taylor