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

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

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.

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.

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.