Overview
- Researchers followed 2,183 dementia‑free adults with an average age of 79 who wore chest heart/activity monitors for about 12 days and were tracked for roughly three years, during which 176 developed dementia.
- Participants with the weakest circadian rest–activity rhythms had nearly 2.5 times the risk of dementia compared with those with the strongest rhythms.
- Each standard‑deviation drop in relative amplitude, a measure of rhythm strength, corresponded to a 54% increase in dementia risk.
- An activity peak at 2:15 p.m. or later was associated with a 45% higher risk compared with earlier peaks, with about 10% versus 7% developing dementia in those groups.
- The study reports associations rather than causation and notes missing data on sleep disorders, with authors calling for trials of circadian interventions such as light exposure or structured routines.