Objectives: The impact of depressive symptoms on cognitive decline in older adults remains unclear due to inconsistent findings in the literature. It is also unclear whether effects of depressive symptoms on cognitive decline vary with age. This study investigated the effect of concurrent, baseline, and average depressive symptoms on cognitive functioning and decline, and examined the interactive effect of age and depressive symptoms on cognition.
Design: Prospective observational design with examination of cognitive performance and depressive symptoms at 1- to 2-year intervals for up to 26 years.
Setting: Baltimore Longitudinal Study of Aging, National Institute on Aging.
Participants: One thousand five hundred eighty-six dementia-free adults 50 years of age and older.
Measurements: Scores over time on the Center for Epidemiologic Studies Depression Scale and measures of learning and memory, attention and executive functions, verbal and language abilities, visuospatial functioning, and general cognitive status.
Results: Increased depressive symptoms were associated with poor cognitive functioning and cognitive decline in multiple domains. Concurrent, baseline, and average depressive symptoms had differential associations with cognition. Average depressive symptoms, a measure of chronic symptoms, seemed to show the most widespread effects on cognitive abilities. Effects of depressive symptoms on some frontal functions were greater with advancing age.
Conclusion: Depressive symptoms are associated with poor cognitive functioning and cognitive decline, particularly with advancing age. The widespread impact of average depressive symptoms on cognition suggests that clinicians should consider the chronicity of depressive symptoms when evaluating cognitive functioning in older adults.