The Swedish occupational fatigue inventory in people with multiple sclerosis.

OBJECTIVES To investigate the applicability of the Swedish Occupational Fatigue Inventory and its ability to identify different dimensions of fatigue in people with multiple sclerosis with varying degrees of disease severity, and the correlation of each of its 5 dimensions with the Fatigue Severity Scale. DESIGN An observational, prospective study. SUBJECTS Two hundred and nineteen outpatients: 59.5% had mild, 17% moderate and 23.5% severe disease severity; 83% received immunomodulatory treatment. METHODS Both questionnaires were administered at inclusion, and at 12 and 24 months. Analyses of internal consistency, item-total correlation, factor analysis and tests of correlations were performed. RESULTS The instrument was completed by 97% of subjects. Internal consistency was satisfactory in the dimensions Lack of energy, Lack of motivation and Sleepiness, but not in Physical exertion and Physical discomfort. Factor analysis revealed that all but 3 items (2 in Physical exertion, 1 in Physical discomfort) loaded satisfactorily in 5 dimensions. Correlations between the dimensions and the Fatigue Severity Scale were low, except for a moderate correlation found for Lack of energy. CONCLUSION The dimensions Lack of energy, Lack of motivation and Sleepiness appear applicable for use in people with multiple sclerosis. Further development of the physical dimensions and studies on the instrument's capacity to measure changes are needed.