How Sleep Affects Dementia

How Sleep Affects Dementia

Is there a connection between sleep and dementia? Poor sleep is associated with several health conditions, from heart disease and obesity to stroke and depression. It negatively impacts our quality of life and overall wellbeing. But how does sleep affect dementia? In this article, we will be exploring the link between sleep and dementia, how sleep quality impacts memory and dementia and common sleep problems in dementia.

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The Link between Sleep and Dementia

Dementia is a leading cause of death and disability among older people worldwide. Alzheimer’s disease is one of the most common forms of dementia. Between 60% and 70% of dementia cases are Alzheimer’s disease.¹ Symptoms of dementia usually begin to occur around the age of 65. People that have a close relative with dementia, have a higher risk of developing the disease later in life. However, this risk can be reduced by adopting healthy lifestyle habits.¹ Such habits include eating healthy, regular exercise, avoiding smoking and drinking alcohol in moderation. Adequate good quality sleep is also part of a healthy lifestyle that may affect dementia risk.¹

Research studies show that inadequate sleep may increase the risk of dementia. This is particularly true for middle aged people. Poor sleep in middle age may be as a result of shift work, insomnia, anxiety or care responsibilities.³ Improving sleep may also be a way of alleviating the symptoms of dementia.¹ However, scientists are still not yet clear of the relationship between sleep and dementia or if there is a causative link. They are yet to determine if sleep problems predispose to dementia or if sleep problems are a sign of early stages of dementia.¹ Studies have shown a link between sleep disorders and the build-up of beta-amyloid and tau proteins, which are toxins responsible for the symptoms of dementia.¹ Beta-amyloid may have a negative impact on sleep and sleep quality. Also, the neurodegeneration associated with dementia causes damage to the areas of the brain that control sleep and sleep-wake cycles.¹

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How Sleep Quality Impacts Memory and Dementia

Sleep disorders such as sleep apnea, insomnia, inadequate or prolonged sleep and sleep disturbance have been linked to cognitive decline and dementia.¹ Sleep apnea is a common sleep disorder affecting approximately 1 billion people worldwide.¹ The most common form of sleep apnea is obstructive sleep apnea, which causes interruption of breathing during sleep and often wakes a person up. Studies show that people with sleep apnea are at an increased risk of several health conditions, including asthma, cardiovascular disease, cancer and more recently, dementia.¹ 

When a person with sleep apnea stops breathing, it causes a reduction in oxygen supply to the brain which is dangerous. Scientists have found that the decreased oxygen level leads to changes in the brain. The temporal lobe, which is vital for memory, is affected in people with sleep apnea. This change is comparable to what obtains in people with dementia.¹ Studies also show that the hippocampus, a complex brain structure with a major role in learning and memory, is reduced in volume in people with sleep apnea. This reduction in volume of the hippocampus is also a feature of Alzheimer’s disease.¹

The mechanism by which inadequate sleep increases dementia risk is related to the deposition of beta-amyloid protein. This protein causes the development of Alzheimer’s disease by forming clusters and clumps that form Alzheimer’s plaques.³ During the day, our brains form beta-amyloid proteins. However, when we sleep, the brain cells and their connections shrink. This allows more space between the brain cells for the beta-amyloid and other toxic substances to be flushed away.³ Therefore, inadequate sleep does not give the brain enough time to remove these substances. As they continue to accumulate, they ultimately lead to dementia.³ Studies show that people who are at increased risk of developing Alzheimer’s disease can benefit from adequate sleep. Better sleep reduces the risk of Alzheimer’s and the accumulation in the brain of substances associated with the condition.³

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Common Sleep Problems in Dementia

Dementia causes sleep disruption in several ways. 

Sleep-wake cycle disorders: the 24 hour cycle that the body goes through each day is known as the sleep-wake cycle. It normally ensures that we are active in the daytime and sleepy at night.² When this pattern is altered for any reason, it causes unusual and disruptive sleep patterns. People with dementia often experience fragmented sleep or in some cases, sleep may become inverted. This means the person is awake all through the night, but then sleeps during most of the day.¹

Alzheimer’s disease patients also experience daytime sleepiness characteristic of the condition, and this is associated with death of key brain cells.¹ Studies show that the sleep disturbance in Alzheimer’s disease may increase the severity of the symptoms of the disease.¹

Light sleep disorders: these are also known as rapid eye movement sleep behaviour disorders. They often cause people to act out their dreams by moving or talking in their sleep.² Light sleep disorders are particularly associated with dementia and Parkinson’s disease. Some studies also show that light sleep disorders may be an early indicator of these disease conditions in older men.²

Sleep disordered breathing: also known as sleep apnoea, sleep disordered breathing occurs when a person has difficulty breathing while asleep.² It may be caused by obstructions to the airway. Sleep disordered breathing is most common in older people and people with obesity. As discussed earlier, people with sleep apnoea may be at a higher risk of cognitive decline and dementia due to reduced oxygen supply to the brain.²

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Source: https://www.shutterstock.com/image-vector/frustrated-old-man-suffer-dementia-loss-2151701803

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References

1. Lang K. (2022). Dementia and sleep: what do we know about this link? Medical News Today. https://www.medicalnewstoday.com/articles/dementia-and-sleep-what-do-we-know-about-this-link
2. Alzheimer’s Society (2023). Sleep and dementia risk. https://www.alzheimers.org.uk/about-dementia/risk-factors-and-prevention/sleep#:~:text=People%20with%20dementia%20often%20have,a%20risk%20factor%20for%20dementia
3. Budson A. E. (2021). Sleep well- and reduce your risk of dementia and death. Harvard Health Publishing. Harvard Medical School. https://www.health.harvard.edu/blog/sleep-well-and-reduce-your-risk-of-dementia-and-death-2021050322508

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