Alzheimer’s: this hidden nighttime disruption begins long before memory loss

What if Alzheimer’s didn’t just erase memories — but also broke the brain’s sense of time? A team of American scientists has discovered that the disease throws off the brain’s internal clock, disrupting the rhythm of the cells responsible for clearing toxic amyloid plaques.

More than 35 million people around the world live with Alzheimer’s, with nearly 10 million new cases each year, according to the Alzheimer’s Research Foundation. Long known for causing memory loss, confusion, and disorientation, the disease also profoundly affects sleep and the body’s natural rhythms.

A new study, published October 23, 2025, in Nature Neuroscience by researchers at Washington University in St. Louis, reveals that Alzheimer’s literally scrambles the brain’s built-in clock.

When the brain’s clock loses its rhythm

In a healthy brain, cells known as microglia and astrocytes follow a steady internal rhythm. This circadian cycle governs hundreds of genes that manage vital cleanup work — clearing amyloid proteins, the infamous plaques linked to Alzheimer’s.

But in mice with the disease, scientists observed a massive breakdown in timing: genes that should turn on and off like clockwork had lost their beat. The result was what the researchers called a kind of “temporal chaos” that blocked the brain’s ability to clear amyloid effectively.

“We found that the circadian rhythm controls about half the genes tied to Alzheimer’s risk,” explained Dr. Erik S. Musiek, neurologist and director of the COBRAS Center at WashU. “When that rhythm goes off track, cells lose coordination and stop performing their jobs when they should.”

In short, the brain begins to lose its sense of time — long before memory problems ever appear.

A new path to slow Alzheimer’s progression

These findings are transforming how scientists think about Alzheimer’s disease. It’s not just that amyloid plaques harm neurons — they also disrupt the very timing of the cells designed to remove them, worsening the cycle of degeneration.

Dr. Musiek and his team believe the key may lie in resetting that inner rhythm. Restoring or stabilizing the brain’s circadian cycles could help microglia function properly and potentially slow the disease’s course. “There’s still a lot we don’t know,” he said, “but the real challenge is learning how to tune the body clock — strengthen it, weaken it, or switch it off in specific cell types.”

Although the study focused on mice, it sheds light on the sleep disturbances common among people with Alzheimer’s. Nighttime awakenings, evening confusion, and reversed day-night cycles may all signal a brain whose biological clock has gone badly out of sync.

For researchers, that insight opens a hopeful new direction: helping the brain restore its rhythm — and maybe, just maybe, slow the disease before memory disappears entirely.

Christelle Cherrier

Web editor

Passionate about words and driven by curiosity, I traded my career as a market research analyst for the sharpened pen of a web writer. For five years, I’ve specialized in health and wellness, delivering clear and insightful content. I’m endlessly fascinated by everything human—from the workings of the body to the mysteries of the mind. My goal? Making complex topics accessible, informative, and engaging—no prescription required!