Self-rated health status as a predictor of death, functional and cognitive impairment: a longitudinal cohort study

Understanding the prognostic capacity of a simple measure of self-rated health (SRH) by older people becomes increasingly important as the population ages. SRH has been shown to predict survival, functional status and service use. The relationship with cognitive impairment has not been widely investigated. This paper investigates SRH as a predictor of death, functional impairment (inability to perform activities of daily living) and cognitive impairment (MMSE < 18) over a 10-year follow-up of participants in the MRC Cognitive Function and Ageing Study. A stratified random sample of 13,004 people aged 65 or over resident in five areas in England and Wales were interviewed. Analysis used data from interviews at baseline, 2, 6 and 10 year follow-up. Hazard ratios for risk of death, functional and cognitive impairment were estimated, unadjusted and adjusted for potential confounding baseline factors. Of the 13,004 participants recruited, 6,882 had died by 10 years and 1,252 and 481 new cases of functional and cognitive impairment respectively were recorded. SRH was associated with a higher risk of death, functional and cognitive impairment. The associations remained after adjustment for age, gender, functional ability and MMSE at baseline: comparing those who rated their health as excellent and good, hazard ratios for risk of death, functional and cognitive impairment were 0.8 (95% CI 0.8-0.9), 0.6 (95% CI 0.5-0.7) and 0.7(95% CI 0.5-0.9), respectively. In-depth qualitative study designs are needed to investigate why the meaning older people give to their health status predicts long-term outcomes.