Disability indicators in the Spanish disability, impairment and health survey

Background: The measurement and meaning of disability depend on the indicators used. In this study the indicators of dependency and severe residual disability are examined on two levels: in each of the 14 selected activities of daily living (ADL) and also as a summary score of the activities count. Methods: The data are extracted of the Disability, Impairment and Health Survey (INE, 1999). The sample is composed of 8.779 entries corresponding to people over 65 years old with disability in some,of the 14 selected ADL. Tables of proportions and contingency have been elaborated, statistics of association and agreement has been calculated and the dimensionality of the aggregated measures had been analyzed through the full information factor analysis. Results: The main discrepancies between the indicators are concentrated on the mobility activities (kappa coefficients ranged between 0,50 to 0,75 for mobility activities and between 0,73 to 0,87 for domestic activities and self-care). Severe residual disability (indicator selected by the National Institute of Statistics) compared to dependency more inability includes more mobility disabled people and excludes more disabled people in domestic activities and self-care.. Dependency more inability is the indicator with the highest validity as a summary measure of disability (two eigenvalues: 8,37 and 1,91, the first factor accounted for 56,3% of the variance, the saturations of the first factor ranged between 0,58. to 0,87). Conclusions: Dependency more inability is more valid than severe residual disability as main indicator of disability.