Measuring disability and function in older women: psychometric properties of the late-life function and disability instrument.

BACKGROUND The recent development of the Late-Life Function and Disability Instrument (LL-FDI) was an important contribution to the measurement of function and disability in older adults. The present study examined the psychometric properties and construct validity of the LL-FDI measure in a sample of older women. METHODS Older black (n = 81) and white (n = 168) women completed the LL-FDI, several measures of physical function, and physical activity measures, and had their body mass index assessed at baseline of an ongoing prospective study. Confirmatory factor analyses (CFA) and correlational analyses were used to examine factorial and construct validity of the measure. RESULTS The CFA, using an iterative model modification technique, resulted in an acceptable 15-item solution for the function component and an 8-item solution for the disability component. This abbreviated instrument demonstrated high correlations with the original scales. Construct validity for the LL-FDI was supported. Participants who demonstrated better physical function, reported being more active, and had lower body mass index reported less disability and less difficulty with function on the LL-FDI. CONCLUSIONS The LL-FDI appears to be an effective instrument for assessing function and disability in older women, and the abbreviated version reported here may prove useful in certain circumstances due to its brevity. However, continued determination of the construct validity of the complete and abbreviated scales is recommended.