Introduction: The objectives of this study were to assess the utility and validity of the self-administered SF-36 and the effect of visual or cognitive impairment on these measures in an older population.Materials and Methods: Attempt rates, completion rates and internal consistency (Cronbach α) were compared within the second cross-sectional, population-based Blue Mountains Eye Study (n = 3509, mean age 66.7 years, 57% women). Results: The SF-36 was attempted by 3162 (90.1%) participants, of which 2470 (78.1%) completed all items and 2873 (90.9%) completed sufficient items for calculation of all dimensions. In a multivariate model adjusting for age, sex, and presenting visual and cognitive impairments, women (P = 0.011) and participants with visual or cognitive impairments (P<0.0001) were less likely to attempt the questionnaire. Completion rates were significantly lower with increasing age (P <0.0001), in men (P ≤0.0005) and in those with cognitive impairment (P <0.0001). A high level of internal consistency (Cronbach α >0.85 for all dimensions) and construct validity was demonstrated, the latter distinguishing between those with and without medical conditions, disabilities or recent hospital admissions (P <0.01). As the prevalence of visual or cognitive impairment was relatively low in this population, we found no apparent effect of these impairments on the validity of SF-36. Conclusions: Attempt and completion rates, but not internal consistency and construct validity, of the SF-36 were influenced by age, gender, and presenting visual and cognitive impairments. The overall high attempt and completion rates, internal consistency and construct validity suggest that the self-administered SF-36 is a suitable health-related quality of life (HRQOL) measure in similar older community-living populations.
The shift towards broader health perspectives and the emphasis on patient preferences have led to the development of many health questionnaires and their inclusion as primary and secondary outcome measures in clinical trials. Measurements of health-related quality of life (HRQOL), a multidimensional concept encompassing physical, emotional and social aspects associated with a disease or its treatment, are increasingly used to organise, finance and deliver health care services for the growing older population.
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