Development, construct validity, and predictive validity of a continuous frailty scale: Results from 2 large US cohorts

Abstract

Frailty is an age-related clinical syndrome of decreased resilience to stressors. Among numerous assessments of frailty, the frailty phenotype (FP) scale proposed by Fried et al. has been the most widely used. We aimed to develop a continuous frailty scale that could overcome limitations facing the categorical FP scale and to evaluate its construct validity, predictive validity, and measurement properties. Data were from the Cardiovascular Health Study (n = 4,243) and Health and Retirement Study (n = 7,600), both conducted in the United States. Frailty was conceptualized as a continuous construct, assessed by 5 measures used in the FP scale: gait speed, grip strength, exhaustion, physical activity, and weight loss. We used confirmatory factor analysis to investigate the relationship between the 5 indicators and the latent frailty construct. We examined the association of the continuous frailty scale with mortality and disability. The unidimensional model fit the data satisfactorily; similar factor structure was observed across 2 cohorts. Gait speed and weight loss were the strongest and weakest indicators, respectively; grip strength, exhaustion, and physical activity had similar strength in measuring frailty. In each cohort, the continuous frailty scale was strongly associated with mortality and disability and continued to be associated with outcomes among robust and prefrail persons classified by the FP scale.