Measurement characteristics for two health-related quality of life measures in older adults: The SF-36 and the CDC Healthy Days items

Abstract

BackgroundThe Short Form Health Survey (SF-36) and the Centers for Disease Control and Prevention (CDC) Healthy Days items are well known measures of health-related quality of life. The validity of the SF-36 for older adults and those with disabilities has been questioned. ObjectiveAssess the extent to which the SF-36 and the Centers for Disease Control and Prevention (CDC) Healthy Days items measure the same aspects of health; whether the SF-36 and the CDC unhealthy days items are invariant across gender, functional status, or the presence of chronic health conditions of older adults; and whether each of the SF-36's eight subscales is independently associated with the CDC Healthy Days items. MethodsWe analyzed data from 66,269 adult Medicare advantage members age 65 and older. We used confirmatory factor analyses and regression modeling to test associations between the CDC Healthy Days items and subscales of the SF-36. ResultsThe CDC Healthy Days items were associated with the SF-36 global measures of physical and mental health. The CDC physically unhealthy days item was associated with the SF-36 subscales for bodily pain, physical role limitations, and general health, while the CDC mentally unhealthy days item was associated with the SF-36 subscales for mental health, emotional role limitations, vitality and social functioning. The SF-36 physical functioning subscale was not independently associated with either of the CDC Healthy Days items. ConclusionsThe CDC Healthy Days items measure similar domains as the SF-36 but appear to assess HRQOL without regard to limitations in functioning.