Cognitive and physical fatigue in multiple sclerosis: relations between self-report and objective performance

Fatigue is one of the most disabling symptoms of multiple sclerosis (MS), but little is known about patients' perceptions of fatigue and changes in their performance on cognitive tasks. To study these relations, 39 patients with clinically definite MS and 19 matched healthy control participants completed baseline self-reports of physical and cognitive fatigue and measurements of grip strength, word list learning, and vigilance. Following 30 min of testing on a cognitive work battery (verbal fluency, Wechsler Adult Intelligence Scale-Revised [WAIS-R] Comprehension, WAIS-R Vocabulary), the baseline measures were readministered. At baseline, MS patients reported more physical and cognitive fatigue than did controls and the MS patients performed more poorly on the grip strength, word list learning, and vigilance tasks. Following cognitive work, the patients reported increased physical and cognitive fatigue, but their objective performance on grip strength, learning, and vigilance was unchangecl from baseline. Controls showed no change in fatigue ratings or performance.