Background: The Barthel Index is one of the most employed questionnaires for the evaluation of functionality, but there is no information on its psychometric properties.
Objective: The aim was to evaluate the reliability, validity, and responsiveness of the Spanish version of the Barthel Index.
Methods: The data employed in this paper were obtained from four Spanish cohorts of elderly people of 60 years or older. We collected data on age, gender, education level, comorbidities, and questionnaires regarding functionality, health-related quality of life, depression, and social support.
Results: The Cronbach's alpha coefficients were greater than 0.70. The confirmatory factor analysis provided satisfactory fit indexes and factor loadings. The correlation coefficients between the Barthel Index and the other questionnaires were lower than the Cronbach's alpha coefficients. Known-groups validity showed significant differences in the Barthel Index according to age, number of comorbidities, and gender. The standardized effect size and the standardized response mean were between 0.68 and 1.81.
Discussion: This version of the Barthel Index has good reliability, its structural validity has been confirmed, and the questionnaire can discriminate between groups and detect changes at follow-up points.
Conclusions: This questionnaire can be used in the evaluation of functionality and basic activities of daily living in elderly people with different conditions.
Keywords: Barthel Index; Functionality; Reliability; Responsiveness; Validity.