Objective: To identify the extent to which exercise intervention studies in multiple sclerosis rehabilitation are addressing comorbidities and if researchers consider comorbidities as possible moderators or mediators of exercise outcomes.
Methods: Five databases were searched from inception to January 8, 2016, for exercise-related terms in combination with multiple sclerosis. Studies were screened and limited to randomized control trials, full text, and English language. We assessed whether comorbidities were excluded or included, how they were reported and described, and if they were examined as possible moderators or mediators of exercise outcomes.
Results: We reviewed 99 articles that included various exercise interventions, where the most common were general multi-faceted exercise training ( n=34), cardiovascular training ( n=18), progressive-resistance training ( n=12), and balance and gait training ( n=12). In total, 77 of 99 studies reported one or more comorbidities as an exclusion criterion. The most commonly excluded comorbidities were cardiovascular diseases, cognitive impairments or psychiatric disorders, and unspecified conditions or contraindications. Only nine studies reported details on excluded participants with comorbidities. Across studies that reported comorbidities of included participants ( n=8), none examined comorbidities as possible moderators or mediators of exercise outcomes.
Conclusion: Although a variety of exercise interventions have positive outcomes, there is limited evidence that these interventions are generalizable to people with multiple sclerosis who have comorbid conditions.
Keywords: Exercise; Multiple Sclerosis; Randomized controlled trial; comorbidities; systematic review.