The predictive validity for mortality of the index of mobility-related limitation - results from the EPESE study

BACKGROUND: self-reported disability reflects physical, environmental and attitudinal factors. We have previously reported the empirical identification of three simple tests to provide an index of (ambulatory) mobility-related physiological limitations (MOBLI). Evidence of the MOBLI 's responsiveness over time has been presented. Evidence of the predictive validity of the index is needed. OBJECTIVE: we aimed to measure the predictive validity for future mortality of the MOBLI and of self-reported mobility disability in a longitudinal cohort study. METHODS: data are from the sixth annual interview for two sites in the Established Populations for Epidemiologic Studies of the Elderly study. Included were 3,040 people, with information about self-reported walking difficulties, walking speed, time to complete five chair stands and peak expiratory flow. Age- and sex-adjusted death rates over a 4-year follow-up were computed, and proportional hazards regression models were used in the analysis. RESULTS: the MOBLI score is associated with subsequent mortality over 4 years, with evidence of a 'dose-response' relationship. The predictive value for mortality of the MOBLI score is similar to that of self-reported mobility disability in the studied population. CONCLUSIONS: the 'objective' MOBLI index has predictive validity as a continuous or dichotomised measure of the physiological component of mobility limitation in older populations. Given its empirical basis and face validity, predictive validity and responsiveness to change, MOBLI should be considered for local validation and use in epidemiological comparisons of older populations across countries or over longer periods of time.