Objective: There is continued uncertainty regarding the strength of association between performance-based and self-report measures of physical functioning, and of their relationship to self-efficacy and health-related quality of life (HRQoL). This study assessed the inter-relationships between such measures, and the predictors of 'physical' aspects of HRQoL in frail older patients.
Design: We used statistical models to determine the predictors of 'physical' HRQoL, according to the physical component summary score and the physical functioning domain of the 36-item short form (SF-36) questionnaire.
Setting: Patients were recruited from hospitals in Australia and New Zealand and followed up in their homes.
Subjects: Two hundred and forty-three frail older patients.
Main measures: Physical functioning was assessed using three performance-based measures (Timed Up and Go Test, gait speed and the Berg Balance Scale) and five self-report measures, including the modified falls self-efficacy scale, at three and six months after registration.
Results: A moderate association (r = 0.48-0.55) was found between each of the performance-based and self-report measures, including the SF-36 physical component summary score. Multiple linear regression analyses showed that the performance-based measures and falls self-efficacy predicted 33% of the SF-36 physical component summary score. Falls self-efficacy was the single highest predictor of both the SF-36 physical component summary score and SF-36 physical functioning domain. A curvilinear relationship was found between the SF-36 physical functioning domain and two variables: falls self-efficacy and the Berg Balance Scale.
Conclusions: Although performance-based and self-report measures provide complementary but distinct measures of physical function, psychosocial factors such as self-efficacy have a strong influence on the HRQoL of frail older people.