The association of depression and mortality in elderly persons: a case for multiple, independent pathways.

Background: The evidence for an association between depression and mortality among community-dwelling elderly persons remains inconclusive, although it is well established for younger individuals. Extant studies suggest that this association weakens when adjusted for potential confounding factors, especially functional impairment. A cohort of elderly subjects followed for 3 years was analyzed to determine the association of depression and 3-year mortality, controlling for the major known risk factors for mortality in the elderly population.
Methods: Information on depression (CES-D scores), mortality, demographics, body mass index, chronic disease, smoking history, cognitive impairment, functional impairment, self-rated health, and social support was obtained from a stratified probability-based sample of community-dwelling elderly persons, with equal distribution between African Americans and whites in the Piedmont of North Carolina. Descriptive statistics were calculated, and logistic regression was used for a series of models with progressively more control variables.
Results: The unadjusted relative odds of mortality among depressed subjects at baseline was 1.98 over 3 years of follow-up. Inclusion of age, gender, and race into the model did not reduce the relative odds. When chronic disease and health habits, cognitive impairment, functional impairment, and social support were added to the model, the odds ratios for mortality with depression were 1.74, 1.69, 1.29, and 1.21, respectively. This decrease in odds ratios was not observed for other variables in the model when additional variables were added.
Conclusions: The estimated odds of dying if depressed moved toward unity as other risk factors for mortality were controlled. Unlike other known risk factors for mortality in the elderly population, depression appears to be associated with mortality through a number of independent mechanisms, perhaps through complex feedback loops.