Study: Alzheimer's sleep disorders may involve immune cell inflammatory response

A new study suggests that sleep disorders common in Alzheimer's patients might be linked to widespread inflammation in the brain, driven by the immune system, rather than solely by the death of neurons or the physical presence of amyloid plaques.

Researchers at the University of Kentucky used mouse models to investigate this connection. Their findings indicate that microglia, the brain's primary immune cells, may inadvertently disrupt overall brain function and sleep when attempting to respond to amyloid plaques. The study likens this reaction to a fire alarm system that, instead of controlling a fire, floods the entire building with water, causing more damage than the initial threat.

The research involved two groups of mice: one genetically predisposed to developing amyloid plaques and a control group of normally aging mice. Brain activity and muscle activity were monitored using electroencephalograms (EEG) and electromyograms (EMG) at different stages of the disease progression. The results showed distinct sleep abnormalities in the mice with Alzheimer's-like conditions.

To test the role of microglia, the researchers administered a drug that blocks signals essential for microglial survival. This treatment temporarily depleted about 87% of the microglia in the Alzheimer's model mice. Following the treatment, the mice regained over two hours of sleep per day on average. Importantly, this sleep improvement did not correlate with a reduction in amyloid plaques, suggesting that the reversible factor affecting sleep is indeed the inflammatory immune response, not the plaques themselves.

While the study provides a new perspective on Alzheimer's-related sleep issues, the researchers emphasize that these findings are based on animal experiments and may not directly translate to humans. The study was published in the journal 'Alzheimer's & Dementia'.