Memory complaints in amnestic Mild Cognitive Impairment: More prospective or retrospective?

Objective: Patients with amnestic Mild Cognitive Impairment (aMCI), usually considered an early stage of Alzheimer's disease, have deficits not only in retrospective memory (RM), that is, recalling of past events, words or people, but also on prospective memory (PM), the cognitive ability of remembering to execute delayed intentions in the future. This study investigated whether patients with aMCI refer more PM complaints as compared with RM complaints, and whether this might depend upon short-term vs long-term items or time-based vs event-based tasks.

Methods: Patients with aMCI (n = 178) and healthy controls (n = 160) underwent the Prospective and Retrospective Memory Questionnaire (PRMQ), a 16-item instrument to appraise differences between PM and RM complaints, as well as a general mental state examination, a subjective memory complaints questionnaire, objective memory tests, and assessment of depressive symptoms and activities of daily living.

Results: Patients with aMCI reported more memory complaints evaluated with the PRMQ (total score = 44.3 ± 10.8) as compared with controls (36.7 ± 9.8, P < 0.001). Using a mixed effect repeated-measures analysis of covariance (ANCOVA) showed that participants generally referred more retrospective than prospective memory complaints. Patients with aMCI had significantly more complaints on short-term memory as compared with long-term memory, and more complaints in time-based (auto-initiated) as compared with event-based tasks, than healthy controls.

Conclusion: Patients with aMCI reported significantly more difficulties on short-term memory, presumably reflecting internal temporal lobe pathology typical of Alzheimer's disease, and more complaints on time-based tasks, which are cognitively very demanding, but did not seem particularly troubled regarding prospective memory.