People with Alzheimer’s disease often struggle with their daily routines.
They may have trouble sleeping through the night, take frequent naps during the day, or become confused and restless in the evening — a condition known as “sundowning.”
These patterns point to a link between Alzheimer’s and the circadian system — the body’s internal clock that controls sleep, wakefulness, and other daily biological rhythms.
Now, scientists at Washington University School of Medicine in St. Louis have found strong evidence that Alzheimer’s disease disrupts this internal clock.
Their study, published in Nature Neuroscience, shows that in mice with Alzheimer’s, hundreds of brain genes stop following their usual daily rhythms. These changes affect key brain cells and could explain some of the disease’s symptoms.
The researchers found that Alzheimer’s alters circadian rhythms in two types of brain cells: microglia, which act like the brain’s cleanup crew, and astrocytes, which help brain cells communicate.
When the internal rhythm breaks down, these cells no longer work in sync, which may prevent the brain from clearing harmful proteins like amyloid. Amyloid buildup is a hallmark of Alzheimer’s.
Dr. Erik Musiek, who led the study, explained that about half of the 82 known Alzheimer’s risk genes are controlled by the circadian system. In healthy brains, these genes turn on and off at certain times of the day.
But in mice with Alzheimer’s, that timing gets thrown off. Instead of switching on or off in a smooth cycle, the genes behave chaotically.
Sleep problems are some of the earliest and most frustrating symptoms for patients and their families. Dr. Musiek’s earlier research showed that sleep issues can start years before memory loss appears.
Poor sleep stresses the brain and may speed up Alzheimer’s progression. By understanding how the body clock is involved, researchers hope to find new ways to slow or stop the disease.
In the new study, researchers looked at how gene activity changes over a 24-hour period in healthy mice and mice with amyloid buildup.
They discovered that the Alzheimer’s-affected mice had major changes in gene rhythms in both microglia and astrocytes. Many of the disrupted genes are needed for microglia to clear out waste and amyloid from the brain.
Interestingly, the study also found that some genes, which normally don’t follow a daily rhythm, began to cycle in Alzheimer’s mice. Many of these newly rhythmic genes are linked to inflammation or stress responses, which suggests the brain may be trying to fight off damage in an unbalanced way.
This research opens the door to new kinds of Alzheimer’s treatments. Instead of just focusing on removing amyloid plaques, scientists might be able to support brain health by restoring circadian rhythms in key brain cells.
Future treatments could involve adjusting how the brain clock works — either strengthening it, resetting it, or changing it in specific cells.
Dr. Musiek says the ultimate goal is to learn how to use the body’s natural rhythms to help prevent or delay Alzheimer’s. While more research is needed, this study brings us one step closer to understanding how deeply our brain’s clock is tied to brain health.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
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