Background. Fatigue is a debilitating symptom in multiple sclerosis (MS) that may be associated with reduced physical activity and increased sedentary behavior. Objective. This study examined the associations among fatigue and device-measured physical activity and sedentary behavior in people with MS. Methods. The participants (n = 252) completed the Patient Determined Disease Steps (PDDS) and Fatigue Severity Scale (FSS) and wore a waist-mounted accelerometer for 7 days. Participants were divided into 2 groups based on fatigue severity as measured by the FSS scale. We compared percentage of wear time spent in sedentary, light physical activity (LPA), and moderate to vigorous physical activity (MVPA) between the 2 groups. Results. Persons in the fatigued group (FSS score ≥ 4) spent a greater percentage of time in sedentary behavior (P = .004) and a lower percentage of time in LPA (P = .035). Persons in the fatigued group further spent a lower percentage of time in nontransformed MVPA (P < .001) and square-root-transformed MVPA (P < .001) than persons in the nonfatigued group. When controlling for PDDS scores and years of education, there were no longer significant differences between groups in sedentary behavior, LPA, or transformed MVPA values; the difference in nontransformed MVPA was still statistically significant but likely the result of nonnormally distributed data. Conclusion. The present study suggests that factors other than fatigue might be associated with physical activity and sedentary behavior in MS, and this group might benefit from focal behavioral interventions that take into account mobility status in persons with MS who have fatigue.
Keywords: fatigue; multiple sclerosis; physical activity; sedentary behavior; symptom.