One of the earliest signs of Alzheimer's might be how poorly you sleep through the night, a new study in mice suggests.
Researchers from the Washington University School of Medicine in St. Louis found that mice with Alzheimer's plaques also experienced sleep abnormalities when those plaques were first developing. The study is published in the journal Science Translational Medicine.
When healthy, the mice used in the study sleep 40 minutes for every daytime hour (since mice are nocturnal). But their sleep time went down to 30 minutes for every daytime hour when the plaques were developing in their brains, the researchers found.
The mice's levels of a protein called amyloid beta -- which makes up the plaques, and levels of which normally go up and down throughout the day and night -- stopped fluctuating when the brain plaques began to develop, the researchers said.
"We suspect that the plaques are pulling in amyloid beta, removing it from the processes that would normally clear it from the brain," study researcher Dr. David M. Holtzman, M.D., the head of Washington University’s Department of Neurology, said in a statement.
In order to confirm that it was in fact the amyloid beta in the plaques that were having the effect on the mice's sleep, the researchers gave another set of mice an amyloid beta vaccine. In these mice, no brain plaques ever developed, their amyloid beta levels fluctuated as normal, and their sleep was not altered at all.
"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," Holtzman said in the statement.
This is not the first time amyloid plaques have been linked with sleeping problems. A previous study from the Washington University School of Medicine in St. Louis showed a link between trouble sleeping -- waking up often in the middle of the night and not being able to fall asleep -- and biomarkers of amyloid beta plaques, MedPage Today reported. That research was presented at the American Academy of Neurology annual meeting.
Sleep problems are a known symptom of Alzheimer's disease. The Sleep Foundation reported:
Another primary symptom of AD is a disrupted sleep/wake cycle, which causes patients to be sleepy during the daytime and alert and restless at night. Because caregivers are likely to be asleep during the night when AD patients are active, sleep/wake disruptions can be a dangerous problem for AD sufferers. In addition, AD patients who do not get enough sleep are more likely to suffer from agitation.