Depressive symptoms, major depressive episode and cognition in the elderly: the three-city study

The relationship between depression and dementia in the elderly has been extensively studied but the tools used to define depressed subjects are heterogeneous between studies. The objective of this study was to examine the relationship between depression and cognitive performances by using multiple measures of depressive state.

A sample of 7,869 nondemented community-dwelling persons aged >or=65 years participated in the study. Depressive symptoms were evaluated by the Center for Epidemiological Study Depression Scale and the Mini-International Neuropsychiatric Interview was used to assess history of major depressive episodes (MDE). Cognitive function was evaluated by several tests including the Mini-Mental State Examination (MMSE), Trail Making Test, Isaacs Set Test and Benton Visual Retention Test.

When studied in separate models, depressive symptoms were significantly related to lower cognitive performances for all neuropsychological tests after adjusting for potential confounders (p<0.0001), whereas subjects with current MDE had significantly lower performances in MMSE and Isaacs Set Test. When studied concomitantly, only high levels of depressive symptoms were related to lower cognitive performance, whereas existence of MDE (past or current) was no longer associated with cognitive performances.

These data suggest that once current depressive symptoms are taken into account, major depression (past or current) is not associated with lower cognitive performances in a community-based sample of elderly people aged >or=65 years.