A-09: Intra-Individual Cognitive Variability as a Mediator of Associations Between MCI and Cognitive Performance in Older Adults With and Without Multiple Sclerosis

Abstract

Objective: Intra-individual cognitive variability (IICV) is an important marker of cognitive functioning in aging and neurological disease. Whether IICV may serve as a pathway to explain the effect of mild cognitive impairment (MCI) on cognition has not been reported. Therefore, we investigated whether IICV mediated associations between MCI and neuropsychological test performance in older adults and whether disease status (multiple sclerosis vs. healthy controls) moderated this mediation effect. Method/Data Selection: Older adults with multiple sclerosis (OAMS: n = 108; mean age = 64.62 ± 4.28 years) and community-residing healthy controls (n = 113; mean age = 67.60 ± 7.07 years) completed neuropsychological testing. IICV was calculated using a coefficient of variation (CoV) that was derived from subtests of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Cognitive outcomes included Trail Making Test Part A (TMT-A), Trail Making Test Part B (TMT-B), and Hopkins Verbal Learning Test–Revised (HVLT-R) delayed recall. We hypothesized that IICV would mediate associations between cognitive status (MCI vs. normal, determined via clinical case conference procedures) and cognitive outcomes, and further evaluated whether mediation effects differed by group status. Results/Data Synthesis: IICV partially mediated associations between cognitive status and performance on TMT-B (indirect effect = −.113, 95% bootstrap CI [−.230, −.020]) and HVLT-R delayed recall (indirect effect = −.147, 95% bootstrap CI [−.267, −.052]). No mediation effect was observed for TMT-A. Group status did not significantly moderate these indirect effects. Conclusions: Disruptions to consistency and regulation of cognitive operations underlie, in part, the negative effects of MCI on complex cognitive tasks in normal and neuropathological aging.