Fatigue in multiple sclerosis: reciprocal relationships with physical disabilities and depression

Objective: To explore relations of fatigue, physical disabilities, and depression in patients with multiple sclerosis (MS) cross-sectionally and over time.

Methods: Ninety-eight MS patients were interviewed twice at an interval of a year. Relationships of physical and mental fatigue, and reduced activity and motivation with depression and physical disabilities were established cross-sectionally by regression analyses and longitudinally by structural equation modelling.

Results: Cross-sectionally, physical fatigue was related with physical disabilities, and mental fatigue was associated with depression. Prospectively, physical fatigue was a predictor of the physical disabilities of a year later. The reverse relationship of physical disabilities predicting the physical fatigue of one year later was, however, not significant, while depression predicted this physical fatigue and reduced activity of a year later. Depression did not predict the later mental fatigue nor was depression predicted by preceding fatigue experiences.

Conclusions: Fatigue in MS should be studied over time as relationships of fatigue with physical and mental health change during the course of a year. Moreover, differentiating in fatigue experiences sheds light on the relationship of fatigue with physical and mental health.