Past Gait Speed as an Independent Predictor of Mortality in Older Adults Beyond Current Gait Speed

Abstract Background We investigated whether past values of gait speed in older adults provide additional prognostic information beyond current gait speed alone. We assessed various models to best describe past and current value for prediction. Methods We used data from the first five yearly rounds of the National Health and Ageing Trends Study, starting from 2011. The cohort consisted of 4289 community-dwelling participants aged 65 years and older. Gait speed was measured at baseline (Y1) and one year later (Y2). Three-year follow-up for mortality started in year 2. We estimated hazard ratios of various models using combinations of Y1 gait speed, Y2 gait speed, and change in gait speed from Y1 to Y2. Results The mean gait speed at year 2 was 0.77 m/s (0.26) and slightly increased by a mean of 0.04 m/s (0.20) from Y1 to Y2. A 0.1 m/s higher gait speed at Y2 was associated with decreased mortality (HR, 0.81 [0.78, 0.84]). Gait speed improvement from Y1 to Y2 decreased mortality (HR, 0.95 [0.92, 0.99] per 0.1 m/s increase). Models including both Y2 gait speed and change indicated that improvement in gait speed was associated with increased mortality (HR, 1.05 [1.00, 1.11]), independently of Y1 gait speed. Conclusions Past gait speed is predictive of mortality, independent of current gait speed, however, gait speed recovery does not completely negate mortality risks. Past gait speed information is a useful measure for risk prediction in older adults, but the direction of time is important for modelling and data interpretation.