Depressive symptoms and cognitive decline in a community population of older persons

Background: An association between depressive symptoms and cognitive decline has been observed in selected cohorts of older people, but studies of defined populations have had conflicting results. Objective: To test whether the level of depressive symptoms predicted the rate of cognitive decline in a biracial community of older persons. Methods: 4392 older people (88% of those eligible) from a defined community in Chicago completed two or three structured interviews at approximately three year intervals for an average of 5.3 years. At the baseline interview, the number of depressive symptoms was assessed with a 10 item version of the Center for Epidemiologic Studies Depression scale. Cognitive function was assessed at each interview with four performance tests, from which a previously established measure of global cognition was derived. Random effects models were used to assess change in cognition and its relation to depressive symptoms, controlling for age, sex, race, education, and baseline cognitive function. Results: Participants reported a median of one depressive symptom at baseline (interquartile range, 0 to 2). For each depressive symptom, the rate of cognitive decline increased by a mean of about 5%. Results were not substantially changed when persons with cognitive impairment at baseline were excluded, or when chronic illness or participation in cognitively stimulating activities was controlled, and the association was not modified by age, sex, race, or education. Conclusions: The results suggest that depressive symptoms predict cognitive decline in old age.