Associations of Usual Pace and Complex Task Gait Speeds With Incident Mobility Disability.

BACKGROUND/
OBJECTIVES: To assess whether gait speed under complex conditions predicts long-term risk for mobility disability as well as or better than usual-pace gait speed.
DESIGN: Longitudinal cohort study. SETTING/PARTICIPANTS: Subsample of Health Aging and Body Composition study with follow-up from 2002 to 2003 to 2010 to 2011, including 337 community-dwelling adults (mean age = 78.5 years, 50.7% female, 26.1% black). MEASUREMENTS: Associations of gait speed measured under usual-pace, fast-pace, dual-task, and narrow-path conditions with mobility disability, defined by any self-reported difficulty walking ¼ mile assessed annually, were tested by Cox proportional hazard models adjusted for demographic and health characteristics. Models were fitted for each walking condition, and R2 statistics were used to compare predictive value across models. Models were repeated for persistent mobility disability, defined as at least two consecutive years of mobility disability.
RESULTS: Mobility disability occurred in 204 (60.5%) participants over the 8-year follow-up. There was a lower hazard of developing mobility disability with faster gait speed under all conditions. Hazard ratios, confidence intervals, and R2 of gait speed predicting mobility disability were similar across all four walking conditions (R2 range = 0.22-0.27), but were strongest for dual-task gait speed (hazard ratio [95% confidence interval], R2 of fully adjusted models = 0.81 [0.75-0.88], 0.27). Results were comparable for persistent mobility disability (R2 range = 0.26-0.28).
CONCLUSION: Slower gait speed under both usual-pace and complex conditions may be a clinical indicator of future risk of mobility disability. These results support the call for increased use of gait speed measures in routine geriatric care. J Am Geriatr Soc 67:2072-2076, 2019.