Physical dimension of fatigue correlated with disability change over time in patients with multiple sclerosis

To determine the value of fatigue in predicting the change in disability status in patients with multiple sclerosis (MS), we realized a prospective population-based cohort study of 196 patients with clinically definite MS. In 2002, baseline data were collected on fatigue (Modified Fatigue Impact Scale), health-related quality of life (SF-36), and disability status (EDSS score). The EDSS scores were determined again at least three years later. Univariate and multivariate analysis were performed to determine the predictive value of different dimensions of fatigue and other variables (depression and SF-36) on the change in disability status. Of the 196 patients, 106 (54%) patients had an unchanged status or improvement and 90 (46%) showed a worsening of disability. After three years, with control for gender, age, and baseline disability status, a high baseline level of physical fatigue was associated with a worsening of disability status, whereas a low baseline level of physical fatigue was associated with the absence of worsening of the EDSS score. Other dimensions of fatigue, depression and SF-36 were not associated with a worsening of disability. A patient's perceived fatigue may be not only a clinically and psychosocially meaningful outcome but also a predictor of objective outcomes such as changes in disability status at three years.