Longitudinal invariance and construct validity of the abbreviated late-life function and disability instrument in healthy older adults

Objective: To cross-validate the psychometric properties of the abbreviated Late-Life Function and Disability Instrument (LL-FDI), a measure of perceived functional limitations and disability. Design: Baseline and 12-month follow-up assessments conducted across the course of a 12-month exercise program. Setting: University research community. Participants: Older healthy adults (N=179; mean ± SD age, 66.43±5.67y) at baseline; 145 were retained at follow-up. Interventions: Not applicable. Main Outcome Measures: LL-FDI and functional performance measures. Results: Factor analyses confirmed the factor structure of the abbreviated LL-FDI, and all subscales met minimal criteria for temporal invariance. Significant correlations also were found between functional limitations subscales and an array of physical function performance measures, supporting the scale's construct validity. Conclusions: The abbreviated LL-FDI with some modifications appears to be temporally invariant in community-dwelling older adults. Additionally, moderate relationships between functional limitations and functional performance provide further support for these being conceptually distinct constructs.