Decades before an Alzheimer’s diagnosis is made, those likely to get the disease show disruptions in sleep patterns, in particular, a lack of deep sleep. So says Ruth Benca, a psychiatrist at the University of California Irvine. Her work has followed the parallels between rapid-eye movement (REM) sleep and the development of Alzheimer’s. Now, researchers at Washington University School of Medicine in St. Louis have found that people who have less slow-wave sleep also have higher levels of the brain protein tau, an indicator for Alzheimer’s.
It’s long been known that people with Alzheimer’s tend to have poor sleep. But scientists now think that that a lack of deep sleep may be a sign of the disease that appears long before cognitive symptoms are apparent.
“What’s interesting is that we saw this inverse relationship between decreased slow-wave sleep and more tau protein in people who were either cognitively normal or very mildly impaired, meaning that reduced slow-wave activity may be a marker for the transition between normal and impaired,” said first author Brendan Lucey, MD, an assistant professor of neurology and director of the Washington University Sleep Medicine Center. “Measuring how people sleep may be a noninvasive way to screen for Alzheimer’s disease before or just as people begin to develop problems with memory and thinking.”
Studies show that amyloid beta protein starts to build plaque in the brain well before memory loss and confusion are evident. Tangles of tau appear after the plaque, but in advance of brain atrophy. While there is currently no cure for the disease, there are medicines that can slow its progression if it is discovered early.
“The key is that it wasn’t the total amount of sleep that was linked to tau, it was the slow-wave sleep, which reflects quality of sleep,” says Lucey. “The people with increased tau pathology were actually sleeping more at night and napping more in the day, but they weren’t getting as good quality sleep.”
In fact, daytime resting in itself was “significantly” tied to high tau levels, meaning that nappers might want to seek further testing. But nap habits alone, or even impaired sleep, don’t mean you’ll get Alzheimer’s.
“I don’t expect sleep monitoring to replace brain scans or cerebrospinal fluid analysis for identifying early signs of Alzheimer’s disease, but it could supplement them,” Lucey said. “It’s something that could be easily followed over time, and if someone’s sleep habits start changing, that could be a sign for doctors to take a closer look at what might be going on in their brains.”
The Chicken or the Egg?
One thing that researchers don’t yet understand is if poor sleep is allowing buildups of amyloid and tau, or if amyloid and tau deposits inhibit deep sleep. However, healthy research subjects who consented to being awakened every hour (!) showed increased levels of amyloid the day after in a study from the National Institutes of Health in Bethesda, Maryland.
While none of us is likely to get a good night’s sleep every time we lay our head on a pillow, it’s worth the effort. Aim for seven hours. Think of it like you do other health initiatives — getting enough exercise, eating well, keeping alcohol consumption moderate, and not smoking. You may not always meet your goals, but aiming for them is a good thing in itself.
Source: Society of Certified Senior Advisors Blog, June 29, 2020