The nonlinear relationship between gait speed and falls: the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly of Boston Study

OBJECTIVES: To examine the relationship between gait speed and falls risk. DESIGN: Longitudinal analysis of the association between gait speed and subsequent falls and analysis of gait speed decline as a predictor of future falls. SETTING: Population‐based cohort study. PARTICIPANTS: Seven hundred sixty‐three community‐dwelling older adults underwent baseline assessments and were followed for falls; 600 completed an 18‐month follow‐up assessment to determine change in gait speed and were followed for subsequent falls. MEASUREMENTS: Gait speed was measured during a 4‐m walk, falls data were collected from monthly post‐card calendars, and covariates were collected from in‐home and clinic visits. RESULTS: There was a U‐shaped relationship between gait speed and falls, with participants with faster (≥1.3 m/s, incident rate ratio (IRR)=2.12, 95% confidence interval (CI)=1.48–3.04) and slower (<0.6 m/s, IRR=1.60, 95% CI=1.06–2.42) gait speeds at higher risk than those with normal gait speeds (1.0–<1.3 m/s). In adjusted analyses, slower gait speeds were associated with greater risk of indoor falls (<0.6 m/s, IRR=2.17, 95% CI=1.33–3.55; 0.6–<1.0 m/s, IRR=1.45, 95% CI=1.08–1.94), and faster gait speed was associated with greater risk of outdoor falls (IRR=2.11, 95% CI=1.40–3.16). A gait speed decline of more than 0.15 m/s per year predicted greater risk of all falls (IRR=1.86, 95% CI=1.15–3.01). CONCLUSION: There is a nonlinear relationship between gait speed and falls, with a greater risk of outdoor falls in fast walkers and a greater risk of indoor falls in slow walkers.