Sleep and the risk of dementia
People living with dementia often have issues with sleep. But the evidence is unclear on whether poor sleep is a risk factor for dementia.
Can poor sleep increase the risk of dementia?
There is some evidence to suggest that a lack of sleep may increase a person’s risk of dementia, but there is not enough to say for sure.
Currently, researchers are not sure how sleep and dementia are linked. Does poor sleep increase dementia risk, or does dementia lead to poor sleep? Some researchers believe that both of these theories could be true, and the relationship could be circular.
More research is needed to understand the link between poor sleep and dementia.
How to reduce the risk of dementia
A lifelong approach to good health is the best way to lower your risk of dementia.
There are some lifestyle behaviours with enough evidence to show that changing them will reduce your risk of dementia.
Treatments for poor sleep and dementia risk
Good quality sleep is linked to good health, including how well the brain works. According to the NHS, adults usually need around seven to nine hours of sleep. However, some people need more sleep than others. Different factors such age and health play a role in how much sleep we need.
Researchers have investigated whether there are effective treatments for poor sleep and whether these treatments can affect dementia risk.
Many treatments that may improve the quality of sleep involve lifestyle changes. Some of these include:
- regular sleep regimes
- regular eating schedules and diets
- taking physical exercise
- ensuring exposure to bright light in the morning
More research is needed to indicate whether these activities have effects on the risk of dementia or disease progression.
Some drug treatments for poor sleep, such as benzodiazepines, have been linked to an increased risk of dementia. However, some Alzheimer's Society-funded work has shown that these drugs do not increase dementia risk.
There are also several drugs that have been trialled to improve sleep. Some doctors may prescribe melatonin, a hormone that is important in maintaining regular sleep-wake cycles. The evidence so far suggests melatonin does not affect the risk of dementia. Please consult your GP before making any decisions about taking sleep medication.
Sleep disorders and dementia risk
The connection between sleep and dementia is complicated. Different types of dementia are associated with different sleep problems.
The phase of sleep where we dream is called rapid eye movement sleep, or REM. During REM sleep, our muscles relax so we don’t move much. However, some people have a condition that causes them to act out their dreams or talk in their sleep. If this is a regular occurrence it is known as rapid eye movement sleep behaviour disorder (RBD).
Dementia with Lewy bodies and Parkinson's disease seem to be particularly associated with RBD. Some studies suggest that it may be a very early indicator of these conditions, particularly in older men. Researchers believe that this is because the part of the brain that controls our muscles during sleep may be one of the first parts to be damaged.
The sleep-wake cycle is the 24-hour cycle that the body goes through each day. It is what makes us active during the day and sleepy at night. When this cycle is altered it causes many unusual and disruptive sleep patterns. These include wakefulness at night and problems falling asleep and staying asleep, as well as drowsiness and napping during the day.
These sorts of sleep disturbances are associated with many kinds of dementia, most notably Alzheimer's disease. They also affect people with Parkinson's disease.
It is thought that the amyloid protein, that builds up in Alzheimer's disease, may disrupt the sleep-wake cycle.
Studies have shown that raised amyloid levels may be associated with poor sleep quality. It is also linked to problems with storing memories while we sleep. Other research indicates that poor sleep may affect the body's ability to clear the toxic amyloid protein from the brain.
This has led to the suggestion that improving sleep quality may have the potential to delay the progression of Alzheimer's disease. However, it is also possible that the changes to the sleep-wake cycle are caused by other changes in the brain, and do not have an impact on the risk of Alzheimer's.
More research is needed to understand the mechanisms linking sleep-wake cycles and Alzheimer's disease.
Sleep-disordered breathing (SDB) is when someone has difficulty breathing when they are asleep. This may be because of obstructions to the airway, making breathing harder work. Sleep-disordered breathing is sometimes called sleep apnoea.
People of all ages can be affected by sleep-disordered breathing, but it is most common in older people and people with obesity. Some research suggests that people who are affected by sleep-disordered breathing may be at higher risk of memory and thinking problems.
Another study saw changes in the size and shape of the brain in people with sleep-disordered breathing, but no change in memory and thinking skills.
Changes to the brain might be caused by sleep-disordered breathing due to changes in levels of oxygen and carbon dioxide in the blood. It may also change the flow of blood to the brain.
A machine called continuous positive airway pressure (CPAP) has been shown by several studies to reduce the consequences of sleep apnoea. Before this treatment can be used, research is needed to indicate with more detail how to use it. For example, how long the treatment should last and what lifestyle changes can be made to help.
Further reading
Alzheimer's Society dementia support line
Call 0333 150 3456.
If you are affected by dementia, worried about a diagnosis or a carer, trained staff are ready to give you the support you need. Opening hours (excluding bank holidays): Mon to Weds: 9am – 8pm, Thurs and Fri: 9am – 5pm, Sat and Sun: 10am – 4pm.
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