Alzheimer's is the most common form of dementia, affecting roughly 5.5 million Americans. The disease involves a decline in cognitive abilities and behaviors, which can present itself as difficulty with memory, reasoning or performing daily tasks. While the cognitive changes are obvious and well characterized, scientists are learning more about the close link between sleep and Alzheimer's.

How Alzheimer's Affects Sleep

An estimated 25-40% of patients with mild to moderate Alzheimer's have some type of sleep disturbance. As the disease progresses, sleep often becomes even more disrupted. It is not unusual for patients with Alzheimer's to have difficulty falling asleep, remaining asleep for long periods of time and staying awake during the day. Sleep medications often don't work and may predispose individuals to falls and other cognitive disturbances. It remains unclear why the disorder affects sleep in the way that it does. However, it is known that certain toxic proteins, known as beta-amyloid and tau, build up in the brains of people that suffer from Alzheimer's. It is possible that the protein not only affects cognitive function, but also affects the brain circuits in charge of sleep.

How Sleep Affects Alzheimer's

There is growing evidence that sleep disturbance and the development of Alzheimer's and other forms of dementia are linked. Perhaps the most compelling evidence comes from a study in animals where sleep was shown to clear out one of the toxic proteins that is responsible for Alzheimer's (read more about it in my recent  blog post about the subject). Another recent study performed on healthy people used a specialized scanner to measure the amount of beta-amyloid in the brain after normal sleep and after a day of complete sleep deprivation. After getting no sleep, the study found that levels of beta-amyloid increased by 5% compared to those that slept normally.

Sleep and the Future of Alzheimer's

The goal of treating dementia is to identify patients as early as possible in order to start treatment. The hope is to one day have medications that can prevent the progression of the disease. The earlier we can identify patients, the better. One of the earliest markers of impending Alzheimer's may be sleep disruption. Studies have found that sleep disruption can precede the symptoms of Alzheimer's by years. But since there are many things that can disrupt sleep, better tests will be needed to identify those that are actually at a high risk of developing Alzheimer's.

The links between Alzheimer's and sleep are numerous. Research is ongoing and it will be fascinating to determine if there is a way to optimize sleep to help people who suffer from this disease.