Microglia Identified as Primary Driver of Sleep Loss in Alzheimer’s Disease

Researchers at the University of Kentucky have identified brain immune cells called microglia as the primary drivers of sleep disruption in Alzheimer’s disease. A study published in the journal Alzheimer’s & Dementia demonstrates that these cells, which normally protect the brain, trigger a cascade of inflammation that mimics a “whole house response,” ultimately keeping the brain in a state of heightened arousal. By temporarily removing these cells in an animal model, researchers successfully restored more than two hours of sleep per night, offering a potential new therapeutic target for the disease.

The Role of Microglia in Sleep Disruption

For years, the scientific community largely attributed sleep loss in Alzheimer’s patients to damaged neurons or the physical accumulation of amyloid plaques. Macauley, Ph.D., an associate professor of physiology at the University of Kentucky College of Medicine, suggests the disruption stems from a broader immune reaction. According to the research, microglia respond to the presence of amyloid plaques by initiating an elaborate inflammatory cascade. Dr. Macauley describes this process as the immune cells “partying all night,” effectively preventing the brain from entering restorative states. While these cells are intended to clear debris, their overactive response appears to create a persistent state of wakefulness.

Experimental Findings and Sleep Restoration

Constantino, Ph.D.—studied two groups of mice: those with a genetic predisposition to amyloid plaques and “wild-type” mice. Using light sheet microscopy and head-mounted electroencephalography (EEG) and electromyography (EMG) devices, the team monitored brain activity and immune cell behavior across different life stages. The researchers utilized a drug called Pexidartinib (PLX3397), which blocks the signaling pathways necessary for microglial survival. After a 14-day treatment, approximately 87% of the brain’s immune cells were temporarily removed. The results were significant:
* Sleep Recovery: Mice with Alzheimer’s pathology regained over two hours of sleep per night.
* Restorative Sleep: The mice experienced longer periods of nonrapid eye movement (NREM) sleep, which is critical for toxin clearance and memory consolidation.
* Independence from Plaques: Notably, these improvements occurred without any change to the volume of amyloid plaques in the brain, suggesting that the immune-driven inflammation is a distinct and potentially reversible cause of sleep loss.

The “Ceiling Effect” and Disease Progression

The study also revealed an unexpected pattern regarding disease severity. Researchers observed that while amyloid plaques continued to accumulate as the mice aged, the sleep disruption did not worsen proportionally.

“The disruptions in sleep and cortical EEG activity that occur at six months, when plaques first emerge, did not worsen by 18 months, despite more than double the amount of plaque burden,” Dr. Constantino noted. This “ceiling effect” suggests that the initial wave of immune activity triggered by early-stage plaques establishes a baseline of sleep deficit that remains stable even as the disease progresses.

Potential for Future Clinical Diagnostics and Treatment

The research team is now shifting focus toward noninvasive interventions. Because the study distinguished between normal aging—which primarily affects REM sleep—and Alzheimer’s-related pathology—which targets NREM sleep—the researchers believe portable EEG systems could eventually serve as accessible, longitudinal biomarkers for early detection.

Regarding future treatments, the laboratory is investigating whether existing medications, such as the diabetes drug Metformin or the antiseizure drug Stiripentol, can modulate microglial energy processing to reduce overactivity without the need to eliminate the cells entirely. By calming these immune cells, researchers hope to improve cognitive function and quality of life for patients before significant memory loss develops.

This work was supported by the National Institute on Aging and the National Institute of General Medical Sciences, with additional funding from the Cure Alzheimer’s Fund and The CART Fund.