Background and aims: Some prospective studies show that depression is a risk factor for cognitive decline. So far, the explanation for the background of this association has remained unclear. The present study investigated 1) whether depression is etiologically linked to cognitive decline; 2) whether depression and cognitive decline may be the consequence of the same underlying subcortical pathology, or 3) whether depression is a reaction to global cognitive deterioration.
Methods: A cohort of 133 depressed and 144 non-depressed older persons was followed at eight successive observations over 3 years. All subjects were participants in the Longitudinal Aging Study Amsterdam (LASA). Depression symptoms were measured by means of the CES-D at eight successive waves. Cognitive function (memory function, information processing speed, global cognitive functioning) was assessed at baseline and at the last CES-D measurement.
Results: The severity and duration of depressive symptoms were not associated with subsequent decline in memory functioning or global cognitive decline. There was an association between both chronic mild depression and chronic depression, and decline in speed of information processing.
Conclusions: These results support the hypothesis that, in older persons, chronic depression as well as cognitive decline may be the consequence of the same underlying subcortical pathology.