Association of Age at Depression Onset with Cognitive Functioning in Individuals with Late-Life Depression and Executive Dysfunction

Objective: To compare patterns of cognitive performance in older adults with late-onset depression (LOD; >= 65 years of age) with that of older adults with early-onset depression (EOD; <65 years). Methods: Participants were 171 adults aged 60 years or older with major depression and executive dysfunction who were participating in a randomized psychotherapy trial. Participants included 72 LOD and 99 EOD individuals. Cognitive performance on measures of verbal learning, memory, and executive functioning were evaluated. Demographic and clinical characteristics, severity of cerebrovascular risk factors, and disability ratings were also compared between groups. Results: The LOD group was older and had fewer previous episodes of depression and lower severity of depression compared with EOD participants. The LOD group demonstrated poorer performance on measures of verbal learning (F(1,161) = 4.28, p = 0.04) and memory (F(1,160) = 4.65, p = 0.03) than the EOD group. Linear regression analysis demonstrated that LOD and fewer years of education were significant predictors of poorer verbal learning (F(7,114) = 6.25, p < 0.001) and memory (F(7,113)=7.24, p < 0.001). Performance on measures of executive functioning, severity of vascular risk factors, and disability ratings did not differ between the two groups. Conclusion: In older adults with depression and executive dysfunction, LOD was associated with poorer performance on measures of verbal learning and memory. Aging-related brain changes associated with LOD may play a more important role, leading to dysfunction in these cognitive domains than a history of recurrent depressive episodes in older adults with a dysexecutive syndrome.