Examining the SF-36 in an older population: Analysis of data and presentation of Australian adult reference scores from the Dynamic Analyses to Optimise Ageing (DYNOPTA) project

Purpose: To examine the psychometric properties of, and present reference scores for the SF-36 using data from a large community sample of older adults. Methods: Data are from the DYNOPTA project. We focus on data from five studies that included the SF-36, providing a sample of 41,338 participants aged 45-97 years. We examine the factor structure of the SF-36 and item-internal consistency. Results: The psychometric properties of the eight scales of the SF-36 were largely consistent with previous research based on younger and/or smaller samples. However, the assumption of orthogonality between the second-order factors was not supported. In terms of age-related effects, most scales demonstrated a nonlinear effect with markedly poorer health evident for the oldest respondents. In addition, the scales measuring aspects of physical health (PH, BP, RP, GH) showed an overall linear decline in health with increasing age. There were, however, no consistent linear age-related differences in health evident for those scales most strongly associated with mental health (MH, RE, SF, VT). Conclusions: The results confirm the structural validity and internal consistency of the eight scales from the SF-36 with an older population and support its use to assess the health of older Australian adults.