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Dementia risk is linked to the strength of your internal clock, a new study reveals. Researchers found that older adults with weaker and more disrupted circadian rhythms—the body’s natural 24-hour cycle—were significantly more likely to develop dementia over a three-year period.
The Body Clock and Brain Health
What does a healthy circadian rhythm look like, and why does it matter for long-term brain health?
Circadian rhythm governs everything from sleep-wake cycles to hormone release, digestion, and body temperature. It’s orchestrated by the brain and heavily influenced by exposure to light. A robust circadian rhythm means your body clock is well-aligned with the day, sending clear signals for optimal function. People with strong rhythms tend to maintain consistent sleep and activity patterns, even when faced with changes in schedule or season.
Conversely, a weak circadian rhythm is more susceptible to disruption from light and schedule changes. Individuals with weaker rhythms are more likely to experience shifts in their sleep and activity times.
“Changes in circadian rhythms happen with aging, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia,” explained study author Wendy Wang, MPH, Ph.D., 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.”
The research, published in Neurology, involved 2,183 participants with an average age of 79 who were dementia-free at the study’s outset. The group comprised 24% Black individuals and 76% white individuals.
How Researchers Measured Circadian Rhythms
Participants wore chest-worn heart monitors for an average of 12 days to track rest and activity. Researchers analyzed the data to assess the strength and patterns of their circadian rhythms. They then followed the participants for an average of three years, during which 176 were diagnosed with dementia.
Researchers focused on measures like relative amplitude—the difference between a person’s most and least active periods—to determine circadian rhythm strength. Higher relative amplitude indicated a stronger rhythm.
Participants were divided into three groups based on their relative amplitude. Among those with the strongest rhythms (high group), 31 of 728 developed dementia. In contrast, 106 of the 727 in the weakest rhythm group (low group) received a dementia diagnosis.
After accounting for factors like age, blood pressure, and heart disease, researchers found that individuals in the low, weaker rhythm group had nearly 2.5 times the risk of dementia compared to those in the high group. Specifically, there was a 54% increased risk of dementia for each standard deviation decrease in relative amplitude.
The study also revealed that individuals whose activity peaked later in the afternoon—2:15 p.m. or later—had a 45% increased risk of dementia compared to those with an earlier peak (1:11 p.m.–2:14 p.m.). Seven percent of the early-peak group developed dementia, compared to 10% of the late-peak group.
A later peak in activity may indicate a misalignment between the body clock and environmental cues like daylight and darkness.
“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.”
The study acknowledged a limitation: researchers lacked information on sleep disorders, such as sleep apnea, which could influence the results.
More information
Wendy Wang et al, Association Between Circadian Rest-Activity Rhythms and Incident Dementia in Older Adults, Neurology (2026). DOI: 10.1212/wnl.0000000000214513
Journal information:
Neurology
Key medical concepts
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American Academy of Neurology
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Weaker body clocks linked to higher dementia risk in older adults (2026, January 5)
retrieved 6 January 2026
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