Abnormal Forgetting Rate from the Recency Portion of a Word-List in Patients with Subjective Cognitive Decline

Background Subjective cognitive decline (SCD) is a self-perceived decline in cognitive functioning, considered at risk for Mild Cognitive Impairment (MCI) and Alzheimer’s Disease (AD). Objective In this retrospective case-control study, we investigated whether the Recency ratio (Rr), a measure of forgetting from the final portion of a word list, can objectify the memory complaints reported by individuals with SCD. Method We administered the 15-word list Recall Test to 54 SCD individuals and 69 healthy controls. Both groups disclosed a recency effect in immediate recall, with a decline in the delayed recall, particularly marked in the SCD group. Results A two-way ANOVA comparing ratio scores across the three portions of the list revealed a significant Group x Position interaction (F = 4.47; p = .01), due to a significantly higher ratio value in the recency portion for the SCD group (F = 4.84; p = .03), while primacy and mid-list ratios were comparable between groups. Conclusions These results, in continuity with previous data in MCI and AD populations, may suggest that, since Rr significantly differs between groups, a possible model including Rr along with other measures may increase accuracy in detecting memory complaints experienced by SCD people. Even if Rr alone cannot predict group classification, our observations could help identify neuropsychological markers useful in the early stages of AD. To our knowledge, this is the first time Rr has been studied in the SCD population, and this makes our data particularly relevant, in that they document a decline that standard neuropsychological tests are not able to detect.