Researchers from the Washington University School of Medicine in St Louis found that when the first signs of Alzheimer's plaques appear in the brain, the normal sleep-wake cycle is significantly disrupted.
"If sleep abnormalities begin this early in the course of human Alzheimer's disease, those changes could provide us with an easily detectable sign of pathology," senior author David M Holtzman, said.
"As we start to treat Alzheimer's patients before the onset of dementia, the presence or absence of sleep problems may be a rapid indicator of whether the new treatments are succeeding," Holtzman said in a statement.
The new research, led by Jee Hoon Roh, a neurologist and postdoctoral fellow in Holtzman's laboratory, showed that when the first indicators of brain plaques appear, the natural fluctuations in amyloid beta levels stop in both mice and humans.
"We suspect that the plaques are pulling in amyloid beta, removing it from the processes that would normally clear it from the brain," Holtzman said.
Mice are nocturnal animals and normally sleep for 40 minutes during every hour of daylight, but when Alzheimer's plaques began forming in their brains, their average sleep times dropped to 30 minutes per hour.
To confirm that amyloid beta was directly linked to the changes in sleep, researchers gave a vaccine against amyloid beta to a new group of mice with the same genetic modifications.
As these mice grew older, they did not develop brain plaques. Their sleeping patterns remained normal and amyloid beta levels in the brain continued to rise and fall regularly.
The study was published in the journal Science Translational Medicine.
