Disrupted daily rhythms may signal higher dementia risk, study finds

Disruptions in the body’s internal clock — the system that governs when we sleep, wake, and stay active — may offer early clues to a higher risk of dementia, a new study suggests.

The research, published in the medical journal Neurology, found that older adults with irregular daily activity and rest patterns were more likely to develop dementia over the following few years. The study was co-led by Wendy Wang, Ph.D., M.P.H., an assistant professor at UT Southwestern Medical Center, along with Lin Yee Chen, M.D., M.S., from the University of Minnesota.

Circadian rhythm, often described as the body’s 24-hour internal clock, helps regulate essential functions such as sleep, hormone release, and metabolism. When that rhythm becomes disrupted, it may affect processes tied to brain health, including inflammation and oxidative stress.

“Among community-based adults, altered rest-activity rhythms — which are markers of circadian rhythms — may be a risk factor for dementia,” Wang said.

A heart monitor with a new purpose

What makes the study stand out is how researchers measured these rhythms. Instead of relying on sleep diaries or wrist-worn fitness trackers, the team used data from a chest-worn ambulatory electrocardiogram (ECG) monitor — a device already widely used to track heart health.

The analysis drew on data from the long-running Atherosclerosis Risk in Communities (ARIC) Study. More than 2,000 older adults without dementia wore the monitor for up to two weeks between 2016 and 2017. Built into the device was an accelerometer that recorded movement throughout the day and night.

Researchers examined several aspects of daily activity, including:

• How strong or regular participants’ activity cycles were
• How fragmented activity and rest were across daytime and nighttime
• When peak activity occurred during the day

Over an average follow-up period of about three years, 176 participants were diagnosed with dementia.

Clear pattern

After accounting for age, education, heart health, and genetic risk factors, the results showed a clear pattern: people with weaker daily rhythms, more fragmented rest and activity, and later peak activity times were more likely to develop dementia.

The study’s participants were, on average, 79 years old, and nearly one-quarter identified as Black — a level of racial diversity that has often been missing from dementia research. That makes the findings especially relevant for understanding risk in real-world, aging populations.

Because ambulatory heart monitors are already commonly used in clinical care, researchers say the data they collect could one day help doctors identify dementia risk earlier — possibly before memory symptoms appear. Still, they caution that more research is needed before this approach can be used routinely.

“Future work assessing circadian rhythms earlier in life is warranted, especially given the long preclinical stage of dementia,” Wang said.

The findings also raise the possibility that strengthening circadian rhythms — through strategies such as consistent sleep schedules, increased daytime activity, light therapy, or other lifestyle changes — could one day play a role in reducing dementia risk.