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OBJECTIVES: To determine whether fast gait speed at study baseline and change in gait speed had independent associations with disability onset.

DESIGN: Cohort study with 11-year follow-up (1999-2010).

SETTING: Three-City Study center, Dijon, France.

PARTICIPANTS: Community-dwelling individuals aged 65 to 85 (N = 3,814, 61% female).

MEASUREMENTS: Fast gait speed (over 6 m) was assessed up to five times and disability (mobility (Rosow-Breslau scale), instrumental activities of daily living (IADLs; Lawton-Brody scale), basic activities of daily living (ADLs; Katz scale)) six times. A hierarchical disability indicator was constructed; participants were considered disabled if they reported difficulties with mobility and IADLs or with mobility, IADLs, and ADLs. The association between baseline fast gait speed and its slope of change and disability incidence was examined using joint models for longitudinal and time-to-event data.

RESULTS: Over follow-up, 628 participants (68% women) developed disability. Mean fast gait speed at baseline was 1.54 m/s, and annual decline was 0.017 m/s. The hazard ratio of disability per standard deviation (SD) (-0.22 m/s) slower baseline fast gait speed was 1.77 (95% confidence interval (CI) = 1.60-1.94) and for one-SD (-0.013 m/s) faster annual decline was 1.38 (95% CI = 1.10-1.73) when both parameters were included in a sex- and age-adjusted model. All associations remained statistically significant in multivariable models, except for slope of change when chronic conditions were added to the model; of chronic conditions, dyspnea was the main contributor.

CONCLUSION: Accelerated decline in fast gait speed was associated with disability independent of baseline fast gait speed. These results confirm the importance of measuring gait speed repeatedly in elderly adults to identify those at higher risk of disability and the need to identify determinants of decline, because they are likely to be targets for prevention and treatment to reduce disability risk.

(C) 2015 by the American Geriatrics Society