How much do depressive symptoms affect cognition at the population level? The Monongahela-Youghiogheny Healthy Aging Team (MYHAT) study

Objective To examine the impact of subjective depressive symptoms on objective performance on tests of several cognitive domains, in a community-based sample of older adults. Methods An age-stratified sample of 2036 individuals aged 65+ years was drawn from the electoral rolls of a U.S. community, excluding individuals with moderate to severe cognitive impairment. A cognitive test battery and a modified Center for Epidemiologic Studies-Depression scale (mCES-D) were completed by 1982 participants. Cognitive test scores were compared across levels of depressive symptoms, and composite scores created to represent cognitive domains of attention, language, memory, visuospatial, and executive function. Multivariable regression models tested the association of depressive symptoms with cognitive domain composite scores, adjusting for age, sex, race, and education. Results Most participants reported no depressive symptoms. Small differences in cognitive scores were observed on all tests among those with 0, 1-2, and >= 3 symptoms. Adjusting for demographic variables, depressive symptoms remained associated with lower performance on all cognitive composites except attention, most strongly with executive function. Depressive symptoms explained <2% of the variance in test scores, less than that explained by age or education. Conclusion In this population-based sample of older adults, restricted to those with normal or only mildly impaired cognition, a relatively small proportion reported any depressive symptoms. The number of depressive symptoms had strong statistically significant associations with performance in most cognitive domains. However, depressive symptoms explained little of the variance in cognitive performance, with relatively small differences in scores among those with and without symptoms. Copyright (C) 2009 John Wiley & Sons, Ltd.