Physical reserve: construct development and predictive utility.

Abstract

Physical reserve (PR) refers to one's ability to maintain physical functioning despite age, illness, or injury. The measurement and predictive utility of PR, however, are not well established. We quantified PR using a residual measurement approach by extracting standardized residuals from gait speed, while accounting for demographic and clinical/disease variables, and used it to predict fall-risk. Participants (n = 510; age ≥ 70ys) were enrolled in a longitudinal study. Falls were assessed annually (in-person) and bimonthly (via structured telephone interview). General Estimating Equations (GEE) revealed that higher baseline PR was associated with reduced odds of reporting falls over repeated assessments in the total sample, and incident falls among those without fall's history. The protective effect of PR against fall risk remained significant when adjusting for multiple demographic and medical confounders. We propose a novel framework to assessing PR and demonstrate that higher PR is protective against fall-risk in older adults.