Fatigue, as measured using the Modified Fatigue Impact Scale, is a predictor of processing speed improvement induced by exercise in patients with multiple sclerosis: data from a randomized controlled trial

Background Few studies have evaluated the impact of physical activity (PA) on cognition and fatigue, and none have considered the effects of PA on the relationship between cognition and fatigue. Objectives We evaluated the effect of PA in people with multiple sclerosis (pwMS) in a 6-month-long single-blind randomized controlled trial. We focused on the impact of exercise on cognition, fatigue, and the relationship between cognition and fatigue. Methods We recruited pwMS, who were then randomly assigned 1:1 to either a PA protocol group or a control group (CG). All patients underwent assessments using the Brief International Cognitive Assessment for Multiple Sclerosis including symbol digit modality test (SDMT), Berg Balance Scale (BBS), gait analysis, 6-Minute Walk Test, Timed Up and Go (TUG) test, and the Modified Fatigue Impact Scale (MFIS) at the beginning of the study (T0), at the end of the study (EOS) 24 weeks after T0, and at 24 weeks following the EOS (FU). Results A Wilcoxon test revealed a significant effect of exercise in the PA group, but not in the CG. Significant differences between T0 and EOS were found in the spatiotemporal parameters of gait, and performance on the SDMT, TUG, BBS, and MFIS. These differences were also present during the FU period. A regression model revealed that the baseline MFIS score predicted processing speed improvement (R2 = 0.65, p < 0.01), as the SDMT T score increased by 0.3 for each one-unit increase in the MFIS score at T0. Conclusion PA affects multiple aspects of the pathology in pwMS. Patients with greater fatigue must not be discouraged from exercise, as they may greatly benefit from PA. Specifically, PA was shown to improve information processing speed.