Pathway from gait speed to incidence of disability and mortality in older adults: A mediating role of physical activity

Abstract

ObjectivesTo determine whether physical activity mediates the association of gait speed with incident disability and mortality in older adults. Study designProspective cohort data from 782 community-dwelling Japanese older adults were analyzed. The median follow-up periods for incident disability and mortality were 4.4 and 4.5 years, respectively. Main outcome measuresPhysical activity was assessed with the Japan Arteriosclerosis Longitudinal Study Physical Activity Questionnaire, gait speed was calculated from 5-m walking time, and incident disability was defined as long-term care insurance certification during follow-up. ResultsThere were 247 cases of incident disability and 202 deaths during follow-up. After adjusting for potential confounders, faster gait speed was associated with decreased risk of incident disability (hazard ratio [HR] = 0.87, 95% confidence interval [CI] = 0.82–0.93), but physical activity level was not associated with incident disability (HR = 0.98, 95% CI = 0.95–1.01). Gait speed was associated with mortality risk in the model without physical activity (HR = 0.93, 95% CI = 0.88–1.00). When gait speed and physical activity were both included in the model, gait speed was not associated with mortality (HR = 0.95, 95% CI = 0.89–1.02) but physical activity was associated with mortality (HR = 0.95, 95% CI = 0.92–0.99). Physical activity was a mediating factor in the association between gait speed and mortality (Sobel test p = .025). ConclusionsGait speed is directly associated with incident disability and is indirectly related to mortality through physical activity in older adults.