A weak body clock may be an early warning for dementia

 People whose daily rhythms were weaker, more fragmented, or shifted later in the day faced a much higher risk of developing dementia. The findings suggest that staying in sync with natural sleep and activity cycles may play a key role in brain health as we age. Credit: Shutterstock

Highlights:

• A large new study suggests the body's internal clock, known as circadian rhythm, may play an important role in dementia risk.
• More than 2,000 older adults wore small monitors for about 12 days, allowing researchers to closely track daily patterns of rest and activity.
• People whose body clocks were weaker or more irregular were significantly more likely to develop dementia over the following years.
• Those whose activity levels peaked later in the day, rather than earlier, showed a 45% higher risk of dementia.
• Researchers say future studies exploring circadian rhythm approaches such as light exposure or lifestyle changes could reveal new ways to reduce dementia risk.

Weaker Body Clocks Linked to Dementia Risk

A new study suggests that disruptions in the body's internal clock may be tied to a higher risk of dementia. Research published on December 29, 2025, in Neurology, the medical journal of the American Academy of Neurology, found that people with weaker and more irregular circadian rhythms were more likely to develop dementia. The study also showed that individuals whose daily activity levels peaked later in the day faced a higher risk than those who peaked earlier. While these findings reveal a strong link, they do not show that circadian rhythm changes directly cause dementia.

What Circadian Rhythms Do in the Body

Circadian rhythm refers to the body's natural timing system. It controls the 24-hour sleep-wake cycle and helps regulate key functions such as hormone release, digestion, and body temperature. This internal clock is directed by the brain and responds to environmental signals, especially light.

When circadian rhythms are strong, the body stays closely aligned with the daily cycle of light and dark. This leads to consistent patterns of sleep and activity, even when schedules or seasons change. In contrast, weaker rhythms make the body clock more sensitive to disruptions. People with less stable rhythms are more likely to shift their sleep and activity times due to changes in routine or daylight.

Aging, Circadian Changes, and Dementia

"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 study author Wendy Wang, MPH, PhD, of the Peter O'Donnell Jr. School of Public Health at UT Southwestern Medical Center in Dallas, Texas. "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."

Source: ScienceDaily