Differences in correlates of fatigue between relapsing and progressive forms of multiple sclerosis.

Background: Fatigue is one of the most prevalent and impactful symptoms for people with multiple sclerosis (MS). Yet, fatigue is less understood in progressive forms of MS, and few studies have explored the extent to which MS disease course is associated with fatigue. The current study aimed to (1) describe fatigue severity and fatigue interference (the extent to which fatigue interferes with individuals' physical, mental, and social activities) in people with progressive MS (primary progressive MS and secondary progressive MS); (2) compare fatigue severity and fatigue interference in people with progressive forms of MS to people with relapsing-remitting MS (RRMS); and (3) identify factors associated with fatigue severity and fatigue interference in people with progressive forms of MS and RRMS.