Measuring functional status: cross-sectional and longitudinal associations between performance and self-report...

We investigated cross-sectional as well as longitudinal associations between performance-based measures of functional status and self-reported measures of functional status. In the Zutphen Elderly Study, 494 men, born between 1900 and 1920, were examined in 1990, of whom 303 were reexamined in 1993. A performance score was constructed on the basis of four tests: standing balance, walking speed, ability to rise from a chair, and external shoulder rotation. Self-reported functional status was based on disabilities in basic activities of daily living, mobility, and instrumental activities of daily living. A hierarchic disability scale was constructed. Cross-sectional correlation coefficients between the performance score and the disability scale were 0.22 in 1990 and 0.39 in 1993. Correlations were highest between the test for walking speed and self-reported mobility and IADL, and between the test for external shoulder rotation and self-reported disabilities in basic activities of daily living. The correlation between the 3-year changes in performance and in self-report was 0.20 (p < 0.001). Both performance and self-report at baseline predicted performance and self-report after 3 years. Performance-based measures of functional status are cross-sectionally and longitudinally associated at modest levels with self-reported disabilities. Performance measures and self-reported measures are complementary, but do not measure the same construct.