Although fatigue does not correlate with life expectancy or the disease course of multiple sclerosis, its presence increases the risk of several psychosocial and socioeconomic complications. Persistent fatigue adversely affects activities of daily living and social interactions, such as housework, shopping, and engagement in social activities (Lerdal et al 2007). Fatigue also has a profound impact on occupational performance. In a study of multiple sclerosis subjects who had reduced their work hours to part-time status, 90% reported fatigue as a primary reason for work status change (Smith and Arnett 2005). As social and occupational functions contribute to quality of life, these aspects should be taken into consideration when assessing the impact of fatigue.