Relationships between changes in time spent walking since middle age and incident disability: The Ohsaki Cohort 2006 Study

Introduction: In comparison with the adults who remain sedentary, those who maintain or increase their physical activity have lower mortality. However, the association between physical activity across the lifespan and incident disability has not been documented. We examined the relationships between changes in time spent walking since middle age and incident disability, using data of a population-based cohort study in Japan. Methods: We conducted a prospective cohort study in 7,177 Japanese individuals aged ≥65 years in 2006. Information on time spent walking was collected via two questionnaire surveys held in 1994 and 2006. Information on mobility limitations and other lifestyle factors was collected in 2006 survey. Data on incident disability were retrieved from the public Long-term Care Insurance database, in which subjects were followed up for 4 years. Cox proportional hazards regression analysis was used to investigate the association between changes in time spent walking and incident disability. Results: The 4-year incidence of functional disability was 9.9% (717 cases). Among those who walked ≤30 minutes in 1994 survey, the multiple-adjusted HR (95%CI) of incident ability were 0.69 (0.49-0.98) among those who walked >30 minutes in 2006 survey, 0.62 (0.34-1.13) among those who walked ≥1 hour in 2006 survey, as compared with those who remained sedentary as walking ≤30 minutes in 2006 survey. Conclusion: Increase in time spent walking among the sedentary adults was significantly associated with a lower risk of incident disability, even after adjusted for possible confounding factors.