Detecting cognitive fatigue in multiple sclerosis: method matters.

ABSTRACT

BACKGROUND: Fatigue is a frequently reported and debilitating symptom in multiple sclerosis (MS). Cognitive fatigue (CF) can be defined as decreased performance with sustained cognitive effort. The effectiveness of the Paced Auditory Serial Addition Task (PASAT) and the Computerized Test of Information Processing (CTIP) at detecting CF was examined, as was the impact of methodology. Subjective fatigue was measured using the Fatigue Impact Scale (FIS). The relationship between objective and subjective fatigue was examined. METHODS: 70 MS and 72 healthy controls (HC) completed the PASAT (3″ and 2″), CTIP, and FIS as part of a larger battery. RESULTS: The MS and HCs performed worse on cognitively demanding tasks. Depending on methodology, PASAT performance varied between groups at the 3″ inter-stimulus interval (ISI) and the MS group showed greater susceptibility to CF as their ability to meet task demands declined as the task progressed. CTIP performance for both groups varied differently over time depending on task. The relationship between subjective and objective measures of fatigue varied depending on methodology, with PASAT generally correlating well with the Cognitive Dimension of the FIS. CONCLUSIONS: The PASAT is a sensitive measure of CF in MS. Additional information is obtained with different scoring methods, with percent dyad scoring method being most sensitive to CF. The ability to detect a relationship between objective and subjective measures varied with methodology.