The association between depressive and cognitive symptoms in amnestic mild cognitive impairment

Background: Depressive symptoms are frequently observed in older adults with mild cognitive impairment (MCI). However, little is known regarding the cognitive characteristics of this important subgroup. Methods: We examined executive functions (controlled inhibition) and verbal episodic memory in 33 healthy older adults (control group), 18 older adults with amnestic MCI plus subclinical depressive symptoms (a-MCI/D+ group), and 26 older adults with amnestic MCI but no depressive symptoms (a-MCI group). Results: Compared to the a-MCI and control groups, patients with a-MCI/D+ showed poor controlled inhibition. Moreover, in verbal episodic memory these patients recalled fewer words than control participants on immediate free, delayed free, and delayed total (free plus cued) recall. Performance on immediate recall suggested a self-retrieval deficit, but delayed performance also revealed the existence of an encoding impairment. In the a-MCI group, participants exhibited normal performance on the executive task, but pervasive memory impairment; the memory deficit concerned free and total recall on both immediate and delayed tasks, suggesting the existence of encoding and self-retrieval disturbances. Conclusions: This study reveals differences between the pattern of cognitive impairment for a-MCI/D+ and a-MCI subgroups particularly at the level of executive capacities. In terms of memory functioning, the differences between the subgroups were more subtle; more studies are needed in order to better characterize the memory impairment of a-MCI/D+ and a-MCI patients.