Systematic, Evidence-Based Review of Exercise, Physical Activity, and Physical Fitness Effects on Cognition in Persons with Multiple Sclerosis.

Cognitive dysfunction is highly prevalent, disabling, and poorly-managed in persons with multiple sclerosis (MS). Recent evidence suggests that exercise might have beneficial effects on cognition in this population. The current systematic, evidence-based review examined the existing literature on exercise, physical activity, and physical fitness effects on cognition in MS to accurately describe the current status of the field, offer recommendations for clinicians, and identify study-specific and participant-specific characteristics for providing future direction for ongoing MS research. We performed an open-dated search of Medline, PsychInfo, and CINAHL in December 2015. The search strategy involved using the terms 'exercise' OR 'physical activity' OR 'physical fitness' OR 'aerobic' OR 'resistance' OR 'balance' OR 'walking' OR 'yoga' OR 'training' OR 'rehabilitation' AND 'multiple sclerosis'. Articles were eliminated from the systematic review if it was a review article, theoretical paper, or textbook chapter; did not involve persons with MS; involved only persons with pediatric-onset MS; did not involve neuropsychological outcomes; did not include empirical data to evaluate outcomes; involved pharmacological interventions; or was not available in English. The selected articles were first classified as examining exercise, physical activity, or physical fitness, and were then randomly assigned to 2 independent reviewers who rated each article for level of evidence based on American Academy of Neurology criteria. Reviewers further completed a table to characterize important elements of each study (i.e., intervention characteristics), the cognitive domain(s) that were targeted, participant-specific characteristics, outcome measures, and study results. The present review resulted in 26 studies on the effects of exercise, physical activity, and physical fitness on cognition in persons with MS. This included 1 Class I study, 3 Class II studies, 8 Class III studies, and 14 Class IV studies. Of the 26 total studies, 6 were randomized controlled trials. Overall, there is conflicting evidence for the effects of exercise on cognition in MS, and overall positive, but not definitive evidence for the effects of physical activity and physical fitness, respectively, on cognition in this population. Collectively, there is insufficient well-designed research to definitively conclude that exercise, physical activity, and physical fitness are effective for improving cognition in MS. This is based, in part, on methodological issues of Class I and II studies, such as inclusion of cognition as a secondary outcome (35 % of reviewed studies), poorly-developed exercise interventions, and paucity of research that included cognitively-impaired MS samples. However, promising evidence from Class III and Class IV studies may be useful for informing the development of better intervention research.