From US News & World Report…
EXPERTS HAVE LONG warned about the negative effects of sleep deprivation, and new research suggests that people with Alzheimer’s disease may be particularly affected.
In a study of mice and humans, researchers at Washington University School of Medicine in St. Louis found that sleep deprivation increases levels of the protein tau, which is linked to Alzheimer’s disease. In follow-up studies in mice, the researchers also found that sleeplessness speeds up the spread of toxic clumps of tau in the brain, a precursor to brain damage and dementia.
The study, published Thursday in the journal Science, suggests that a lack of adequate sleep can advance Alzheimer’s while good sleep could help maintain brain health.
“The interesting thing about this study is that it suggests that real-life factors such as sleep might affect how fast the disease spreads through the brain,” Dr. David Holtzman, senior author and head of the medical school’s neurology department, said in a statement.
Tau is a protein normally found in the brain, even in healthy people, but it starts to cause problems when it clumps together in tangles. Those clumps injure nearby brain tissue and are a sign of coming cognitive decline.
Researchers found that, in mice, tau levels were about twice as high during times when they were awake and active. When the mice were disturbed during times they were typically asleep or resting, their tau levels doubled.
The team found that humans reacted similarly to sleep disturbances. Researchers collected brain and spinal cord fluid from eight people after a normal night of sleep and then again after a night when they were kept awake all night. After the sleepless night, tau levels in the subjects’ brain and spinal cord fluid rose by about 50 percent.
The results suggest that tau is typically released in brains during waking hours by thinking and doing things and the release is then slowed during sleep, allowing tau to be cleared away, the researchers said. Disrupting sleep interferes with this pattern, causing tau to build up and making it more likely that it will start clumping in toxic tangles.
Researchers also found evidence that these tangles spread further in the brain when subjects were kept awake.