ST. LOUIS — While an occasional restless night is no cause for concern, ongoing sleep changes can be a warning sign of Alzheimer’s disease. Recently, scientists researching slow-wave sleep and specific brain proteins have found a better explanation for why poor quality sleep can be linked to the brain changes associated with Alzheimer’s disease.
Slow-wave sleep is that all-important deep sleep we need to reinforce our memories and help us wake up feeling refreshed. Researchers at Washington University School of Medicine have found that people who are getting insufficient slow-wave sleep have higher amounts of the brain protein tau, which is linked to Alzheimer’s disease.
“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,” explains lead author Brendan Lucey, a professor of neurology and director of the university Sleep Medicine Center, in a statement. “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.”
Researchers studied the sleep habits of 119 people aged 60 and older. The majority of participants (80 percent) were cognitively normal while the rest were very mildly impaired.
The sleep habits of participants were monitored in their normal home setting. Researchers gave participants portable EEG monitors to strap to their foreheads to measure their brain waves as they slept and wristwatch-like sensors that tracked their body movements. Participants were also asked to keep sleep logs that included both nighttime sleep and daytime napping.
Researchers also measured levels of amyloid beta and tau in the brain and in the cerebrospinal fluid. Amyloid beta protein collects into plaques in the brain early on before the appearance of tangles of tau protein, a hallmark of severe cognitive decline.
The majority (104 participants) underwent spinal taps to measure for both amyloid beta and tau proteins in their cerebrospinal fluid. About a third (38 participants) underwent PET scans to measure the amounts of the two proteins in their brains. About one-quarter (27 participants) did both tests.
Study authors believe the link they have found between poor quality sleep and increases in tau protein warrant additional research into the importance of sleep monitoring. They suggest that just a few simple questions, such as “How much do you nap during the day?” could be an easy, inexpensive way for doctors to pinpoint who might need additional testing.
“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,” says Lucey.
“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.”
Findings were published in the Jan. 9, 2019 issue of Science Translational Medicine.