Validity and Interpretation Thresholds of Habitual and fast Gait Speed for Preclinical Mobility Limitation in Middle-aged and Older Adults

Objectives: Current guidelines for preclinical mobility limitation (PCML) screening recommend habitual and fast gait speed testing; however, comparative evidence on their discriminative accuracy is limited, and empirical gait speed thresholds for PCML have not been established. We aimed to (i) compare habitual and fast gait speed on their discriminative ability and (ii) derive interpretation thresholds for PCML among community-dwelling middle-aged and older adults. Design: In this cross-sectional study, 235 participants (mean[SD], 68[7.3]years) completed the 4-metre gait speed assessment. PCML classification was based on questions regarding the use of compensatory stair gait strategy. Results: In multinomial regression, reduced habitual and fast gait speed were associated with increased odds of “PCML likely” (versus “PCML unlikely”): adjusted interquartile-range odds ratios (95%CI) were 2.6 (1.2-5.7) and 5.8 (1.5-22.5) for habitual and fast gait speed, respectively. Fast gait speed showed greater discriminative ability (pairwise AUC [95%CI], 0.80 [0.68-0.92]) than habitual gait speed (0.74 [0.62-0.87]). The interpretation thresholds (95% CI) for PCML were 1.24 m/s (1.20-1.31m/s) and 1.67m/s (1.61-1.78m/s) for habitual and fast gait speed, respectively. Conclusions: Fast gait speed was more adept than habitual gait speed in differentiating between individuals with and without PCML, and empirically-derived thresholds were estimated to complement existing cut-points for PCML.