Depressive symptoms and cognitive decline in older adults

Objectives:Few studies have examined the impact of late-life depression trajectories on specific domains of cognitive function. This study aims to delineate how different depressive symptom trajectories specifically affect cognitive function in older adults.Design:Prospective longitudinal cohort studySetting:Australia and the United States of AmericaParticipants:In total, 11,035 community-dwelling older adults with a mean age of 75 yearsMeasurements:Depressive trajectories were modelled from depressive symptoms according to annual Centre for Epidemiological Studies Depression Scale 10 (CES-D-10) surveys. Four trajectories of depressive symptoms were identified: low ("nondepressed"), consistently mild ("subthreshold depression"), consistently moderate ("persistent depression"), and initially low but increasing ("emerging depression"). Global cognition (Modified Mini-Mental State Examination [3MS]), verbal fluency (Controlled Oral Word Association Test [COWAT]), processing speed (Symbol Digit Modalities Test [SDMT]), episodic memory (Hopkins Verbal Learning Test – Revised [HVLT-R]), and a composite z-score were assessed over a subsequent median 2 years.Results:Subthreshold depression predicted impaired performance on the SDMT (Cohen's d −0.04) and composite score (−0.03); emerging depression predicted impaired performance on the SDMT (−0.13), HVLT-R (−0.09), 3 MS (−0.08) and composite score (−0.09); and persistent depression predicted impaired performance on the SDMT (−0.08), 3 MS (−0.11), and composite score (−0.09).Conclusions:Depressive symptoms are associated with later impaired processing speed. These effects are small. Diverse depression trajectories have different impacts on cognitive function.