Measuring functional status: Cross-sectional and longitudinal associations between performance and self-report (Zutphen Elderly Study 1990-1993)

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.