Rates and predictors of mortality in an aging, rural, community-based cohort - The role of depression

Context: Depression, functional disability, cognitive impairment, and self-rated health all predict mortality in the elderly population. There is no consensus on their relative contributions when examined together. Objectives: To measure rates and identify predictors of mortality in an aging community-based cohort. Design: Ten-year prospective epidemiological study. Predictor variables examined in Cox proportional hazards models were self-rated health, ability to perform instrumental activities of daily living (IADLs), depressive symptoms, and cognitive functioning, controlling for age, sex, education, and number of prescription drugs. Setting: A largely blue-collar rural community in southwestern Pennsylvania. Participants: A population-based cohort of 1064 adults, 67 years or older at the beginning of follow-up. Main Outcome Measures: Mortality at 3, 5, and 10 years (133, 218, and 482 deaths, respectively). Results: Mortality rates were similar to those of the 1990 US population. Older age, male sex, IADL disability, and number of prescription drugs measured at baseline were significant predictors of mortality at all 3 follow-up end points. Depression at baseline predicted earlier (3- and 5-year) mortality but not later (10-year) mortality. The interaction between self-rated health and depression independently and strongly predicted mortality at all end points. Cognitive functioning predicted mortality only when IADL disability was excluded from the model. Conclusions: Age, sex, depression, and functional disability are strong and consistent independent predictors of mortality in older adults in the community, in addition to objective medical burden (prescription drugs). Depression alone predicts mortality in the shorter rather than longer term, but in combination with poor self-rating of health, it strongly predicts mortality at all end points.