Sleep problems are among the most common and disruptive symptoms experienced by people with Alzheimer’s disease. For years, researchers have linked these disturbances to brain damage and the buildup of amyloid plaques. However, new findings suggest that another factor may play a much larger role: the brain’s own immune system.
Scientists at the University of Kentucky have discovered that microglia — specialized immune cells that protect the brain — may be responsible for triggering the sleep disruption associated with Alzheimer’s disease.
The study suggests that these cells, while designed to defend the brain, can become overactive when responding to amyloid plaques. Instead of restoring balance, they may create a chain reaction of inflammation that interferes with normal sleep patterns.
Brain’s defense system may become part of the problem
Microglia act as the brain’s built-in maintenance team. They remove damaged material, respond to threats, and help maintain healthy brain function.
When amyloid plaques begin accumulating, microglia move into action. Researchers now believe that this immune response may become excessive, keeping the brain in a state of heightened activity.
Rather than the plaques themselves directly causing sleep problems, the immune reaction surrounding them may be the main source of disruption.
“This changes the way scientists think about Alzheimer’s-related sleep loss,” researchers noted. The findings suggest that controlling inflammation may be just as important as addressing amyloid buildup.
Study shows sleep improves when Microglia are reduced
To investigate the role of microglia, researchers studied mice genetically programmed to develop Alzheimer’s-like brain changes.
The animals underwent detailed sleep monitoring using technologies that measured brain waves and muscle activity. These recordings allowed scientists to track different sleep stages and identify changes caused by disease progression.
Researchers then used a medication called Pexidartinib (PLX3397) to temporarily reduce the number of microglia in the brain.
After treatment, the mice recovered more than two additional hours of sleep each night. They also showed improvements in deep, restorative nonrapid eye movement (NREM) sleep.
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The improvement occurred without reducing amyloid plaque levels, suggesting that the inflammatory response — rather than plaque quantity alone — may be a key factor affecting sleep.
Early immune activation may set the stage for long-term problems
One surprising discovery was that sleep disruption did not continue getting worse as Alzheimer’s pathology progressed.
Researchers expected that increasing plaque levels would lead to increasingly severe sleep problems. Instead, they found that the biggest disruption occurred when plaques first appeared.
Even when plaque levels later increased significantly, sleep problems remained relatively stable.
This suggests that the first immune response triggered by early plaque formation may establish a lasting change in brain activity.
Alzheimer’s affects the sleep stage most important for recovery
The study also revealed that Alzheimer’s-related changes specifically interfere with deep NREM sleep.
Unlike normal aging, which often reduces REM sleep associated with dreaming, Alzheimer’s pathology appears to target the restorative sleep stage responsible for memory support, brain repair, and waste removal.
Deep sleep plays a critical role in maintaining brain health. During this stage, the brain clears unwanted substances and strengthens important connections involved in learning and memory.
Disruption of this process may create a harmful cycle in which poor sleep contributes to further brain stress and disease progression.
A new approach: Calming Microglia instead of eliminating them
Although removing microglia improved sleep in the study, researchers say the long-term goal is not to eliminate these cells.
Microglia are essential for normal brain function, so future treatments will likely focus on preventing them from becoming excessively activated.
The research team is now exploring whether existing medications, including Metformin and Stiripentol, may help regulate microglial activity and reduce harmful inflammation.
If successful, these approaches could provide a way to protect brain function while preserving the important roles of immune cells.
EEG technology could help detect Alzheimer’s earlier
Beyond treatment possibilities, the study may also contribute to earlier diagnosis.
Researchers identified patterns in brain electrical activity that may help separate Alzheimer’s-related changes from normal aging.
Portable EEG devices could eventually offer a simple, affordable way to monitor brain health outside specialized medical centers. This could allow earlier screening and intervention for people at risk of developing Alzheimer’s disease.