Researchers at the University of Kentucky have identified the brain's own immune cells as the primary driver of sleep loss in Alzheimer's disease, and demonstrated that temporarily removing these cells can restore more than two hours of sleep per day, even when amyloid plaques remain untouched.
The study, published in Alzheimer's & Dementia, challenges decades of assumptions. Scientists had long attributed sleep disruption in Alzheimer's patients to dying neurons or the physical clutter of amyloid plaques in the brain. The Kentucky team, led by associate professor Shannon L. Macauley and first author Nicholas J. Constantino, found that the real culprit is microglia, the brain's resident immune cells.
When microglia detect amyloid plaques, they launch what Macauley described as "an elaborate cascade of inflammation, as if the microglia are partying all night, and keeping the brain awake". The researchers compared the process to a kitchen fire triggering a building-wide sprinkler system, where an overblown immune response turns a local problem into widespread damage.
The team studied two groups of mice at six months and again at 18 months of age using EEG and EMG recordings. When a drug was used to temporarily eliminate most microglia, the animals regained more than two hours of daily sleep despite the plaques remaining unchanged. Macauley called the finding "paradigm shifting" and said it points to an entirely new treatment target for Alzheimer's disease.