Randomized Controlled Trial of Physical Activity and Cognition in Persons with Multiple Sclerosis

Background: Slowed cognitive processing speed is common, debilitating, and difficult to manage in persons with multiple sclerosis (MS). Researchers have recently advocated for physical activity as a behavioral approach for managing slowed cognitive processing speed in MS.

Objectives: The present study adopted a randomized controlled trial (RCT) design and examined the effect of a physical activity behavioral intervention on cognitive processing speed among persons with MS who have mild or moderate disability status.

Methods: 82 MS patients were randomly allocated into intervention or wait-list control conditions. The intervention condition received a theory-based program for increasing physical activity behavior that was delivered via the Internet and one-on-one video chat sessions with a behavior-change coach. Participants completed self-report measures of physical activity and disability status, and underwent the oral Symbol Digit Modalities Test (SDMT) before and after the 6-month period.

Results: Mixed model ANOVA indicated a significant time × condition × disability group interaction on SDMT scores (p = .02, partial-η² = .08), such that persons with mild disability in the intervention condition demonstrated a clinically meaningful improvement in SDMT scores (~6 point change). Further, among those who received the intervention, changes in physical activity were positively associated with changes in SDMT scores in persons with mild (ρ = .45, p = .04), but not moderate (ρ = -.12, p = .33) MS disability, such that greater increases in physical activity were associated with greater improvements in SDMT scores.

Conclusions: The current study supports physical activity as a promising tool for managing cognitive impairment in persons with MS and suggests that physical activity might have specific effects by disability status on cognition in this population.