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• Posted January 2, 2026

Internal Body Clock Linked To Dementia Risk

Sleep problems might be an early warning sign of dementia, a new study says.

Circadian rhythms that are weaker and more fragmented are tied to an increased risk of dementia, researchers reported Dec. 29 in the journal Neurology.

In fact, people with weak circadian rhythms have a more than doubled risk of dementia, results showed.

“Changes in circadian rhythms happen with aging, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia,” said lead researcher Wendy Wang, an assistant professor of epidemiology and internal medicine at UT Southwestern Medical Center in Dallas.

“Our study measured these rest-activity rhythms and found people with weaker and more fragmented rhythms, and people with activity levels that peaked later in the day, had an elevated risk of dementia,” she said in a news release.

Circadian rhythm is another term for the body’s internal clock, which regulates a person’s 24-hour sleep cycle.

Guided by the brain and influenced by light exposure, circadian rhythm also regulates body functions like hormone release, digestion and body temperature.

A strong circadian rhythm aligns a person’s body clock well with the 24-hour day, sending clear signals for body functions, researchers said. People with a strong circadian rhythm tend to follow regular times for sleeping, even if their schedule changes or daylight shifts with the seasons.

On the other hand, people with weak circadian rhythms are more likely to have their body clock disrupted by seasonal shifts or schedule changes, researchers said.

For this study, researchers tracked nearly 2,200 people with an average age of 79. None had dementia at the start of the study.

All participants wore small heart monitors stuck to their chest for an average of 12 days. These monitors captured data on people’s circadian rhythms.

The folks were then followed for around three years on average, during which 176 were diagnosed with dementia.

Based on their circadian rhythms, researchers divided participants into three groups. They then compared the strong circadian and weak circadian groups.

In all, 106 of 727 people in the weak circadian group developed dementia, compared to 31 of 728 people in the strong circadian group, the study found.

That amounted to a nearly 2.5 times higher risk of dementia among people with weaker circadian rhythms, researchers estimated.

Dementia risk also was higher among people whose circadian rhythms peaked later in the afternoon, researchers found.

People whose rhythms peaked around 2:15 p.m. or later had a 45% increased risk of dementia compared to those who peaked between 1:11 p.m. and 2:14 p.m., results showed. 

Having a later peak in activity could mean the body clock is misaligned with seasonal changes in light.

“Disruptions in circadian rhythms may alter body processes like inflammation, and may interfere with sleep, possibly increasing amyloid plaques linked to dementia, or reducing amyloid clearance from the brain,” Wang said.

“Future studies should examine the potential role of circadian rhythm interventions, such as light therapy or lifestyle changes, to determine if they may help lower a person’s risk of dementia,” she added.

More information

The Cleveland Clinic has more about circadian rhythms.

SOURCE: American Academy of Neurology, news release, Dec. 29, 2025