Overview
- Researchers analyzed wearable rest-activity data from more than 2,000 older adults over about 12 days and followed them for a median of three years, during which 176 developed dementia.
- Those with the weakest circadian rhythms had nearly 2.5 times the risk of dementia compared with the strongest group, with risk rising about 54% per standard deviation decrease in rhythm strength.
- Timing mattered: participants whose daily activity peaked after roughly 2:15 p.m. had a 45% higher risk than those whose peak came earlier in the afternoon.
- The authors propose that circadian misalignment may influence inflammation, disrupt sleep, or impair amyloid clearance, but they stress that the findings do not prove causation.
- The study did not account for sleep disorders, and the team calls for controlled trials of light therapy and routine changes to test whether improving rhythms can lower risk.