Dementia risk: A new study suggests that a person’s internal body clock, known as the circadian rhythm, may be tied to the risk of developing dementia, with more disrupted and irregular rhythms associated with a greater likelihood of the condition.
Researchers found that older adults whose daily activity patterns peaked later in the day had a higher risk of dementia than those whose rhythms peaked earlier. In particular, activity peaks occurring after mid-afternoon were linked to a 45% increase in dementia risk compared with earlier peaks.
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The study analysed data from more than 2,100 older adults, with an average age of 79, who did not have dementia at the start of the research. Participants wore chest monitors that tracked rest and activity for an average of 12 days. They were then followed for three years, during which 176 participants were diagnosed with dementia.
A strong circadian rhythm typically aligns well with the 24-hour day, producing consistent daily patterns of sleep and activity. Researchers said people with stronger rhythms tend to keep more stable sleep and wake times, even when schedules or seasons change. By contrast, weaker rhythms were described as more easily disrupted by changes in light exposure or routine, and more likely to drift with seasonal or schedule shifts.
According to the findings, participants with the weakest circadian rhythms had nearly 2.5 times the risk of developing dementia compared with those with the strongest rhythms.
Study author Wendy Wang of the University of Texas Southwestern Medical Center said circadian disruption may affect body processes such as inflammation and sleep, which could influence the build-up of amyloid plaques, protein clumps often seen in Alzheimer’s disease, or reduce the brain’s ability to clear them.
The analysis also reported a difference tied to the timing of peak daily activity. People whose activity peaked at 2:15 p.m. or later were more likely to develop dementia than those whose peak occurred earlier in the afternoon, between 1:11 p.m. and 2:14 p.m.
Researchers said a later activity peak may reflect a mismatch between the body’s internal clock and external cues like daylight and darkness. They noted that circadian rhythms naturally change with age, and growing evidence suggests disruptions may be linked to neurodegenerative disease risk.