Mediating effect of cognitive reserve on associations between processing speed and memory in older adults with and without multiple sclerosis.

OBJECTIVE: Slower processing speed is implicated in memory impairment in both aging and multiple sclerosis (MS). Cognitive reserve serves as a buffer against memory decline and dementia, but no studies have reported on its mediating effect on the associations between processing speed and memory. Therefore, we investigated whether cognitive reserve mediated the relationship between processing speed and verbal memory in older adults and whether the presence of MS modified this association. METHOD: Older adults with MS (n = 104; Mage = 64.84 ± 4.36 years) and healthy controls (HCs: n = 105; Mage = 68.33 ± 7.24 years) underwent neuropsychological testing and brain magnetic resonance imaging. Cognitive reserve was derived using residuals from a regression model predicting a modified total score of the Repeatable Battery for the Assessment of Neuropsychological Status from demographic and brain integrity variables. Processing speed was assessed via the oral Symbol Digit Modalities Test, and memory via the Hopkins Verbal Learning Test-Revised. RESULTS: Cognitive reserve fully mediated the association of Symbol Digit Modalities Test on Hopkins Verbal Learning Test-Revised: immediate recall when fully adjusted for covariates (indirect effect: b = 0.221, 95% bootstrap CI [0.120, 0.322]). For delayed recall, cognitive reserve partially mediated this association in adjusted models (b = 0.221, 95% bootstrap CI [0.124, 0.322]). Group status (i.e., older adults with MS vs. HC) did not significantly moderate the mediating effect of cognitive reserve on either outcome. CONCLUSIONS: Cognitive reserve mediated associations between processing speed and memory performance in older adults with and without MS, highlighting its protective role against memory decline. (PsycInfo Database Record (c) 2025 APA, all rights reserved).