The relationship between subjective fatigue and cognitive fatigue in advanced multiple sclerosis.

The present study examined the cognitive performance and ratings of subjective fatigue in people with advanced MS and matched healthy control participants. A continuous n-back task, involving attention (0-back), was performed at the beginning and end of one testing session; a task involving working memory (1-back) was performed at the beginning and end of another testing session. Subjective fatigue was rated at regular intervals during each session. Overall, there was limited evidence of objective cognitive fatigue in the MS group, as assessed by the change in n-back performance during the sessions. The MS group did report a greater increase, than the control group, in the level of subjective fatigue during the 1-back testing session, but change in subjective fatigue did not correlate significantly with change in cognitive performance. The implications of these findings for our understanding of cognitive fatigue in MS are discussed.