Background: Amnestic mild cognitive impairment (aMCI) and late-life depression (LLD) are associated with increased risk of Alzheimer's disease (AD). This is also true for aMCI with concomitant depressive symptoms (aMCI/D+), but few studies have investigated this syndrome.
Objectives: We aimed to clarify the association between cognitive and depressive symptoms in individuals at risk for AD by examining episodic memory for emotional stimuli in aMCI, aMCI/D+, and LLD.
Methods: Participants were 34 patients with aMCI, 20 patients with aMCI/D+, 19 patients with LLD, and 28 healthy elderly adults. In an implicit encoding task, participants rated the emotional valence of 12 positive, 12 negative, and 12 neutral words. Immediately and 20 minutes later, participants recalled as many words as possible. They were also asked to identify previously presented words during a yes/no recognition trial.
Results: At immediate recall, aMCI participants displayed better recall of emotional words, particularly positive words. aMCI/D+ and control participants displayed better recall of positive and negative words compared to neutral words. LLD participants recalled more negative than neutral words. At delayed recall, emotional words were generally better-remembered than neutral words by all groups. At recognition, all subjects responded more liberally to emotional than to neutral words.
Conclusion: We find that the type of emotional information remembered by aMCI patients at immediate recall depends on the presence or absence of depressive symptoms. These findings contribute to identifying sources of heterogeneity in individuals at risk for AD, and suggest that the cognitive profile of aMCI/D+ is different from that of aMCI and LLD. Future studies should systematically consider the presence of depressive symptoms in elderly at-risk individuals.
Keywords: Aging; Alzheimer’s disease; dementia; depression; emotion; episodic memory.