The 24-Hour Movement Behavior Composition and the Risk of Dementia.

Objectives: This study examined the relationship between the 24-hour movement behavior composition-including sleep, sedentary time, light physical activity, and moderate-to-vigorous physical activity-and dementia risk.

Methods: 93,781 participants (mean age: 62 years) from the UK Biobank were studied. The average daily time spent in each movement behavior was determined using accelerometers. Incident cases of dementia were identified over an average 9.6-year follow-up. Cox proportional hazards models with compositional covariates assessed the associations of interest.

Results: Relative time in moderate-to-vigorous and light physical activity were negatively associated with dementia risk while relative time in sedentary behavior was positively associated with dementia risk. Each 15 min/day reallocation of time from sedentary behavior into sleep, sedentary behavior, or physical activity reduced dementia risk by 2% to 5%.

Conclusions: The time-use composition of movement behaviors across the 24-hour day influences dementia risk.