The relationship between subjective reports of fatigue and executive control in Multiple Sclerosis

Previous studies failed to show a relationship between fatigue and cognitive performance. We used a theory-based Delayed Item Recognition (DIR) paradigm to examine the hypothesis that subjective reports of fatigue and executive control processes were related in MS. Participants were 20 individuals diagnosed with definite diagnosis of MS with Relapsing-Remitting course and 20 controls case matched for age, sex, education and IQ. The DIR paradigm manipulated executive demands in three conditions: Alone, Partial Interference (PI), and Complete Interference (CI). Fatigue was assessed using the Fatigue Severity Scale (FSS). Results: ANOVA Repeated measures analyses showed that DIR performance was slower and less accurate as a function of MS and increased executive demands across the three task conditions. Separate linear regressions revealed that fatigue was related to DIR reaction time and accuracy performance only in the CI condition where executive demands are maximized, and only in the MS group. The present study provided first behavioral evidence that fatigue and executive control are uniquely related in MS. (C) 2009 Elsevier B.V. All rights reserved.