Objective: Recent studies report an association between depressive symptoms and cognitive impairment in old age. The neurobiologic basis of this association is unknown. The authors examined whether cerebral infarcts (present in 55 persons) accounted for the association of depressive symptoms with cognitive impairment in a group of 153 older Catholic nuns, priests, and brothers (67 with dementia and 86 without dementia).
Methods: Subjects underwent detailed clinical evaluations and brain autopsy at death.
Results: Mean values for depressive symptoms during the time of participation were associated with level of cognitive functioning proximate to death in analyses that controlled for age, sex, education, and Alzheimer disease (AD) pathology. The association of depressive symptoms with cognitive functioning was essentially unchanged after controlling for cerebral infarctions, which suggests that depressive symptoms, cerebral infarctions, and AD pathology were independently related to cognitive function. Similar results were found in analyses with episodic memory, semantic memory, working memory, perceptual speed, and visual-spatial ability. The results did not change in analyses examining the volume or location of cerebral infarctions.
Conclusions: These data suggest that cerebral infarctions do not account for the association of depressive symptoms with level of cognitive functioning. The neurobiologic basis for this association remains to be elucidated.