Fatigue, depression, and physical activity in relapsing-remitting multiple sclerosis: Results from a prospective, 18-month study

Background: Fatigue, depression, and physical inactivity are common in multiple sclerosis (MS), but there is limited information on the bi-directional associations among those variables over a long period of time. Objective: This study examined the hypothesis that fatigue and depression would predict change in physical activity and that physical activity would predict changes in fatigue and depression over an 18-month period of time in persons with MS, even after controlling for disability status, disease duration, sex, and age. Methods: This longitudinal study collected data on fatigue, depression, physical activity, and confounding variables from the same sample of persons with relapsing-remitting MS on two occasions that were separated by 18 months. Results: The cross-lagged path coefficient between baseline fatigue and follow-up physical activity was statistically significant (path coefficient =-.26, p < .0001) as was the cross-lagged path coefficient between baseline physical activity and follow-up fatigue (path coefficient=-.11, p < .05). Those bi-directional associations were independent of depression, disability status, disease duration, sex, and age. There were no statistically significant cross-lagged path coefficients between depression and physical activity. Conclusions: This study identified bi-directional associations between fatigue and physical activity over an 18-month period of time. The nature of such associations opens the door for research on fatigue management as an approach for sustaining or promoting physical activity over time.