The role of verbal episodic memory in progression to mild cognitive impairment: The influence of serial position effects

BACKGROUND: Subjective cognitive decline (SCD) may be linked to subtle memory loss. The aim of this study was to determine the influence of verbal episodic memory measures, particularly serial position effects, on the progression from SCD to mild cognitive impairment (MCI). METHODS: Study participants (N = 315), aged ≥ 50, diagnosed as cognitively unimpaired (CU) (N = 211) or with SCD (N = 104) at baseline and then classified as Stable or Worsening at follow-up, were compared using measures from the California Verbal Learning Test (CVLT). ANCOVA was used to compare SCD and CU performance at baseline; General Linear Models (GLMs) with repeated measures were used to compare groups at baseline and at follow-up, considering age, years of education, depressive symptoms, and time between assessments as covariates. RESULTS: SCD participants were older, had fewer years of education, more depressive symptoms, and more subjective cognitive complaints than CU participants. There were no differences between groups at baseline in any of the cognitive measures. The GLMs revealed that the baseline performance of CU and SCD participants who worsened was already poorer than that of the stable participants in free recall measures; only the Worsening SCD participants had significant poorer recall of middle position items at baseline than Stable participants. CONCLUSION: Free recall CVLT measures at baseline can effectively identify progression of cognitive decline in participants without cognitive objective impairment, and the middle position effect at baseline can differentiate SCD participants who will progress to MCI and those who will remain stable.