title: Fatigue, depression, and physical activity in relapsing-remitting multiple sclerosis: Results from a prospective, 18-month study.
abstract: 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.
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA. Electronic address: robmotl@illinois.edu.
authors: Robert W
authors: RW
authors: Motl
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA.
authors: Yoojin
authors: Y
authors: Suh
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA.
authors: Madeline
authors: M
authors: Weikert
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA.
authors: Deirdre
authors: D
authors: Dlugonski
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA.
authors: Swathi
authors: S
authors: Balantrapu
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 350 Freer Hall, Urbana, IL 61801, USA.
authors: Brian
authors: B
authors: Sandroff
keywords: Depression; Fatigue; Longitudinal; Multiple sclerosis; Physical activity; Symptom