Time spent walking and disability-free survival in older Japanese: The Ohsaki Cohort 2006 Study

The extent to which long disability-free survival (DFS) time can be extended according to the amount of time spent walking has not been investigated. The aim of this study was to examine the association between time spent walking per day and DFS time in older adults. We conducted a cohort study of 14 342 disability-free individuals (aged >= 65 years) living in Ohsaki City, Japan. The amount of time spent walking per day (<0.5 h, 0.5-1 h, >= 1 h) by each individual in 2006 was assessed by a self-reported questionnaire. Data on 11-year incident functional disability were retrieved from the public Long-Term Care Insurance database. After estimating the multivariable-adjusted hazard ratios (HRs) of the composite outcome (incident functional disability or death), the multivariable-adjusted 50th percentile differences (50th PDs; difference in the period until the first 50% of the composite outcome occurred) were estimated according to time spent walking. Among 114 764 person-years, the composite outcome occurred in 7761 persons (67.6 per 1000 person-years). The HRs (95% confidence intervals) of the composite outcome were 1.00 (reference) for <0.5 h, 0.84 (0.79, 0.88) for 0.5-1 h, and 0.78 (0.74, 0.83) for >= 1 h (p-trend < 0.001). The 50th PDs (95% confidence intervals) of DFS time were 238 (155, 322) days longer for 0.5-1 h and 360 (265, 454) days longer for >= 1 h, in comparison with <0.5 h. The results suggest that longer time spent walking per day contributes to longer DFS time.