LAUSR

OBJECTIVE The purpose of the study was to estimate, using an isotemporal substitution model, the effect of replacing sedentary behavior (SB) with physical activity on the incidence of disability in community-dwelling older adults. METHODS This 2-year longitudinal cohort study enrolled 3691 community-dwelling older adults (57.2% women; mean age = 74.0 [SD = 5.0] years). Individuals with dementia, stroke, Parkinson disease, depression, low Mini-Mental State Examination scores, dependence on basic activities of daily living, and missing data were excluded. Physical activity and potential confounding factors were investigated as a baseline survey of disability incidence, defined by Japanese long-term care insurance certification, for 2 years in 2 regions. Physical activity data (SB, light-intensity physical activity [LPA], and moderate- to vigorous-intensity physical activity [MVPA]) were measured using triaxial accelerometers for 14 days, and daily mean time spent in each physical activity parameter was computed in increments of 10 minutes. The relationship between baseline physical activity and disability incidence adjusted for potential confounders was analyzed using multilevel Cox proportional hazards regression analyses with an isotemporal substitution model. RESULTS The disability incidence rate was 3.8%, excluding individuals who could not be followed up. Replacing 10 minutes of SB per day with MVPA was associated with a decreased disability incidence (hazard ratio = 0.870; 95% CI = 0.766 to 0.988), whereas no evidence was found for replacing SB with LPA (hazard ratio = 0.980; 95% CI = 0.873 to 1.10). CONCLUSIONS Replacing SB with MVPA was associated with a lower risk of disability. These findings are helpful for establishing disability prevention strategies. IMPACT These results suggest that feasible changes in daily behavior, such as replacing 10 minutes of SB with MVPA daily, might have a protective effect on disability incidence. Clarifying these associations is useful for developing disability prevention strategies and may help reduce the incidence of disability in community-dwelling older adults.