ST. LOUIS — Alzheimer’s telltale body clock disruptions often occur years before noticeable memory loss and other symptoms, a new study reveals. The finding could help doctors pinpoint patients at the greatest risk of developing the disease well in advance.
Researchers from Washington University in St. Louis showed that disturbances to one’s body clock — also know as your circadian rhythm — occur far earlier in people whose memories are intact, but whose brains show early signs of Alzheimer’s disease. Damage in the brain from the condition can start 15 to 20 years before symptoms begin.
For the study, the authors recruited 189 older, cognitively normal adults (about 66 years old on average) and tested them for signs of Alzheimer’s disease. Participants were given PET scans and researchers looked for signs of amyloid plaques in their brains, which are known to lead to Alzheimer’s. Others had cerebrospinal fluid tested for other proteins related to the condition.
They found 139 showed no signs of the disease and most of them had normal sleep/wake cycles.
The other 50 participants, who showed preclinical signs of Alzheimer’s, all experienced significant sleep disruptions, both in how much rest they got each night and how active they were during the day.
The study subjects wore sleep trackers — small devices similar to workout trackers — and kept a sleep diary.
“It wasn’t that the people in the study were sleep-deprived,” explains the study’s first author Erik S. Musiek, an assistant professor of neurology, in a media release. “But their sleep tended to be fragmented. Sleeping for eight hours at night is very different from getting eight hours of sleep in one-hour increments during daytime naps.”
Those who had short periods of activity and rest during both the day and night were more likely to have amyloid plaques detected in their brains.
To further test this finding, the authors regularly disrupted the circadian rhythms of mice over a two-month period. After scanning the rodents’ brains, they found that mice that had their circadian rhythms disrupted had far more amyloid plaques in their brains than those that were not disrupted.
“The mice also had changes in the normal, daily rhythms of amyloid protein in the brain. It’s the first data demonstrating that the disruption of circadian rhythms could be accelerating the deposition of plaques,” says Musiek.
The authors say it’s still too early to formulate chicken-and-egg hypotheses as to whether Alzheimer’s precursors cause circadian rhythm disruption, or if sleep disruption somehow leads to Alzheimer’s.
They plan on continuing to follow the progress of the study’s participants and see whether or not they do in fact go on to develop Alzheimer’s.
The study’s findings were published in the Journal of Experimental Medicine.