Self-reported versus performance-based measures of physical function: prognostic value for survival
Rosero Bixby, Luis
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Background: Although previous studies have indicated that performance assessments strongly predict future survival, few have evaluated the incremental value in the presence of controls for self-reported activity and mobility limitations. Objective: We assess and compare the added value of four tests -- walking speed, chair stands, grip strength, and peak expiratory flow (PEF) -- for predicting all-cause mortality. Methods: Using population-based samples of older adults in Costa Rica (n = 2290, aged 60+) and Taiwan (n = 1219, aged 53+), we estimate proportional hazards models of mortality for an approximate five-year period. Receiver Operator Characteristic (ROC) curves are used to assess the prognostic value of each performance assessment. Results: Self-reported measures of physical limitations contribute substantial gains in mortality prediction, whereas performance-based assessments yield modest incremental gains. PEF provides the greatest added value, followed by grip strength. Our results suggest that including more than two performance assessments may provide little improvement in mortality prediction. Conclusions: PEF and grip strength are often simpler to administer in home interview settings, impose less of a burden on some respondents, and, in the presence of self-reported limitations, appear to be better predictors of mortality than do walking speed or chair stands. Comments: Being unable to perform the test is often a strong predictor of mortality, but these indicators are not well-defined. Exclusion rates vary by the specific task and are likely to depend on the underlying demographic, health, social and cultural characteristics of the sample.