It is very difficult to detect this neurodegenerative disease. By the time it gets diagnosed, it often could not be slowed down anymore.
Researchers from Washington University in St. Louis (WUSTL) and Knight Alzheimer’s Disease Research Center (ARDC) sought out better ways to identify the onset of Alzheimer's disease as early as possible. They believed that altered sleep patterns can serve as a possible marker for the changes in the brain linked with the disease.
Slow-wave sleep is a deep sleep that creates long-term memories and rejuvenates the brain. Losing out on slow-wave sleep increases the amount of tau, a harmful protein linked with brain damage, loss of cognitive abilities, and Alzheimer's disease.
"Since problems with thinking and memory begin as tau increases, we think that slow-wave activity will be an important marker for Alzheimer’s disease [and] that changes in the brain during Alzheimer’s disease, especially tau accumulation, will disrupt normal slow-wave activity either before or soon after problems with thinking and memory start," said WUSTL researcher Brendan P. Lucey, the main author of the study. (Related: Scientists still don’t understand what causes Alzheimer’s but are beginning to see it as a “whole body” problem that manifests in the brain.)
Does one's sleeping patterns affect the risk of early Alzheimer's disease?
The study involved 119 adults who are at least 60 years old. Most of the participants displayed normal brain functions at the start of the study. Only 20 percent of the study group displayed mild cognitive problems.
Each participant evaluated his or her sleep at home. They measured their brain waves using a portable EEG monitor, while a wearable electronic sensor on the wrist kept track of their body movement.
In addition, they also recorded their sleep patterns throughout the entire day. This included nighttime sleep that produced deep sleep and much shorter daytime naps.
For their part, the WUSTL-Knight ARDC researchers evaluated the levels of tau and amyloid beta in the brain of the participants. They also evaluated samples of cerebrospinal fluid taken from the participants.
Like tau, amyloid beta is a protein that is connected with Alzheimer's disease. The plaque formations found in the brain of an Alzheimer's patient are made from accumulated amyloid protein.
Instead of taking daytime naps, get more undisturbed sleep at night
In the report published in the journal Science Translational Medicine, the researchers discovered that the brains of people with lesser amounts of slow-wave sleep showed increased concentrations of tau in their brain. At the same time, their cerebrospinal fluid displayed higher tau-to-amyloid ratios.
Furthermore, daytime napping appeared to be strongly linked to greater levels of tau. This particular result led Lucey to propose that potential patients should be asked about the number of naps they took during the day for comparison with their nighttime sleep.
This seemingly innocuous question could better determine if the patient should undergo further testing for cognitive decline. Earlier studies have shown a connection between disturbed sleep and alterations to the brain caused by Alzheimer's disease.
"I think that the type of sleep monitoring that may play a future role in screening for Alzheimer’s disease still needs to be worked out, but we think slow-wave activity is a potentially sensitive marker worth pursuing in future studies," he warned. "Unfortunately, research has not yet shown that treating sleep disorders will decrease someone’s risk of Alzheimer’s disease."
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