017-22 – Recency ratio in story recall predicts left hippocampal volume in older adults with and without cognitive impairment

Objective: The recency ratio (Rr) is the ratio between immediate and delayed recency recall performance. We have previously suggested that higher Rr scores are related to a reduction in long-term retention, possibly as a result of diminished consolidation, which, in turn, is thought to depend upon hippocampal function. We applied Rr to story recall and tested whether it predicted hippocampal grey matter volume in older adults.
Methods: We analysed data from 290 participants (age = 64.4, 10.6) taken from the Wisconsin Alzheimer’s Disease Research Center database, who were classified as cognitively unimpaired, as having MCI, or Alzheimer’s Disease. Story recall was measured with the Logical Memory Test (LMT), using scores from both baseline and closest visit to MRI scan. Linear regression analyses were carried with left or right hippocampal grey matter volume as outcomes separately, and with Rr, Immediate LMT score, Delayed LMT, or Total ratio (Tr) score as predictors, in separate analyses. False discovery rate was applied to p values.
Results: Baseline and closest to MRI scan Rr scores were significantly associated with left hippocampal volume only (p=.044; p=.004; respectively). Immediate and Delayed LMT scores were not significantly associated with either volume. Baseline and closest to MRI scan Tr scores were also significantly associated with left hippocampal volume only (p=.008; p=.004; respectively).
Conclusions: Rr in story recall outperforms traditional story recall-derived memory scores as a marker of hippocampal grey matter volume, but not total ratio; suggesting the link could be due to total forgetting and not to recency forgetting.