주관적기억장애 환자의 미래계획기억: 예비 연구

Abstract

Background: Subjective memory impairment (SMI), defined by memory complaints with normal age-, gender- and education-adjusted cognitive performance, is a frequent phenomenon in elderly people. According to longitudinal studies, SMI is probably a predictor for future mild cognitive impairment (MCI) and dementia. However, there has been no objective neuropsychological test for evaluating SMI, and previous studies relied solely on patients’ subjective complaints. Thus, our goal was to make an objective standard that is useful in distinguishing SMI from normal aging as well as MCI by considering prospective memory (PM) as a higher level of memory. Methods: The study participants included seven healthy controls, 25 individuals with SMI and eight patients with amnestic MCI (aMCI). The inclusion criteria for SMI were 1) over 55 yr, 2) sustained subjective memory complaints, 3) normal general cognition, 4) no abnormality (within-1SD) in neuropsychological battery and 5) no depression. aMCI was followed by Pitersen’s criteria. To assess prospective memory, the Cambridge Behaviour Prospective Memory Test, which consisted of four time-based and four event-based tasks, was performed. Subsequently, scores from Korean Mini-mental Status Examination (K-MMSE), the 20 min delayed recall Seoul verbal learning test (SVLT), and individual task scores of PM and total PM scores were compared among each group. Results: There were no significant group differences in age, education, sex, K-MMSE score and time-based PM among the three groups. However, SVLT scores and total PM scores showed a significant decline in the aMCI group, unlike that for the SMI and control groups. Moreover, eventbased PM score was significantly decreased stepwise in both SMI and aMCI groups. Conclusions: These findings suggest that PM, especially for event-based tasks, is sensitive for detecting the earliest cognitive changes associated with SMI, and PM tasks seem to be more susceptible to the early cognitive decline than retrospective memory tasks. As PM is a sensitive predictor for future cognitive decline, SMI may be a first manifestation of future dementia in the elderly regardless of depression. Future research will help determine the clinical usefulness of PM tasks.