Cognitive Reserve and Symptom Experience in Multiple Sclerosis: A Buffer to Disability Progression Over Time?

Abstract

ObjectiveTo investigate the possible buffering effect of cognitive reserve on symptom experience for multiple sclerosis (MS) disease course. DesignSecondary analysis of longitudinal data from the North American Research Committee on MS Registry. SettingRegistry study and web-based supplemental survey. ParticipantsPeople with MS (N=859). InterventionsNot applicable. Main Outcome MeasuresTwo health outcome measures, the Symptom Inventory and the Performance Scales, were collected biannually over 1 and 6 years, respectively. Active and passive cognitive reserve was measured using the Stern Leisure Activities and the Sole-Padulles Childhood Enrichment tools, respectively. Linear regression, chi-square, multilevel random-effects modeling, and classification and regression tree modeling were used to compare cross-sectional means, disease course by cognitive reserve, longitudinal trajectories, and active cognitive reserve item endorsement by disability groups, respectively. ResultsPatients with high-active reserve had a lesser symptom burden than those with low-active reserve independent of passive reserve (P<.01). Cognitive reserve was associated with course of disease, such that high-active patients were overrepresented among relapsing-remitting patients, and underrepresented among patients with progressive disease (χ2=14.7, P<.03). Longitudinal modeling revealed a significant interaction of active reserve and time in mobility, fatigue, and overall disability in the whole sample (P<.05 in all comparisons). Among patients whose disability trajectories changed over time, active cognitive reserve was associated with less deterioration (P<.001). Passive cognitive reserve evidenced no effect in the longitudinal analyses. Active cognitive reserve scores across disability groups had a similar range but comprised different items, indicating that patients maintain active cognitive reserve with different activities as the disease progresses. ConclusionsOur findings suggest that active cognitive reserve is a buffer for functional limitation across disability groupings. Cognitive reserve may provide an alternative lens for thinking about the disease course of MS, providing a longer “runway” until disability accrual through cortical remodeling. Loss of cognitive reserve may explain the onset of progressive disease in MS.