The Relationship Between Sleep and Alzheimer’s Disease

We have known for some time about the importance of sleep and how the lack of sleep can have detrimental effects on us. Sleep deprivation can affect our nervous systems, our memories, and the severity of physical and mental health disorders. Not to mention our moods!

Scientists have been studying the relationship between sleep and Alzheimer’s disease and have come up with some interesting findings. This article appears in the July 2018 issue of Science News with the headline, “The Clean Cycle: The body may use sleep as a time to wash away the waste that can cause Alzheimer’s disease.”

The article cites many studies, some with conflicting results. One of the issues that makes definitive conclusions difficult to ascertain relates to the chicken and egg conundrum. Alzheimer’s disease is known to cause difficulty sleeping. And it also appears that interrupted sleep might influence the development of Alzheimer’s. How do we know which comes first?

Neuroscientist Barbara Bendlin has been studying the brain as Alzheimer’s develops. She does this by using the Wisconsin Registry for Alzheimer’s Prevention, which is comprised of more than 1,500 people who were ages 40 to 65 when they signed up. Seventy percent of the registry members have a family history of Alzheimer’s disease but none of them had symptoms themselves when they signed up.

Since 2001, these participants have been tested regularly for memory loss and other signs of Alzheimer’s, such as the presence of amyloid-beta, a protein fragment that can clump into sticky plaques in the brain. These plaques are a hallmark of Alzheimer’s disease. The subjects have also filled out comprehensive questionnaires which include the question, “How tired are you?”

In a 2015 study published in Neurobiology of Aging, Bendlin and other researchers focused on 98 people from the registry who recorded their sleep quality and had brain scans. Those who slept poorly tended to have more A-beta plaques visible on brain imaging.

This study is part of a growing body of research that suggests a sleep-deprived brain might be more vulnerable to Alzheimer’s disease. Animal studies have shown levels of plaque-forming A-beta plummet during sleep. Other research points to the fact that a sleeping brain runs the “clean cycle” (a reference to a dishwasher) to remove the day’s metabolic debris, specifically A-beta plaques. A study done in 2017 found that even one sleepless night appears to leave behind an excess of the troublesome protein fragment.

While this is all impressive research, scientists believe there are still plenty of gaps. Basically, there’s not enough evidence yet to know the degree to which sleep might make a difference in the disease, and study results are not consistent.

A 2017 analysis of studies found that poor sleepers appeared to have approximately a 68 percent higher risk of Alzheimer’s than those who were rested. But we’re back to the chicken and egg question. What comes first?

More research is needed. However, we do know that approximately one-third of American adults are sleep deprived (sleeping fewer than seven hours a night) and the number of people with Alzheimer’s disease is increasing. Certainly, a good night’s sleep could benefit us all.

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