Correlation of self-assessed fatigue and alertness in multiple sclerosis

Background: Fatigue is the most common symptom in multiple sclerosis patients, but is difficult to measure; quantification thus relies on self-assessed questionnaires. Objective: To evaluate a battery of neuropsychological tests regarding their capacity to objectify self-reported fatigue. Methods: We assessed the correlation between age, gender, education, Kurtzke's Expanded Disability Status Scale, depression, fatigue and neuropsychological testing using a cross-sectional approach in 110 multiple sclerosis patients. Fatigue was measured with the Fatigue Severity Scale. Cognition was measured using a series of neuropsychological tests including three subtests of the Test of Attentional Performance, the Brief Repeatable Battery of Neuropsychological Tests and the Faces Symbol Test. Results: According to the Fatigue Severity Scale 51.4% of the cohort were fatigued (scores >= 4). Age, education and depression showed a significant correlation with the Fatigue Severity Scale. Only 5.5% of the cohort exhibited cognitive impairment in the Brief Repeatable Battery of Neuropsychological Tests scores. After correction for age, education, Expanded Disability Status Scale and depression, Fatigue Severity Scale scores were an independent predictor of performance in the alertness subtest of the Test of Attentional Performance (standardized coefficient beta = 0.298, p = 0.014). Conclusion: The alertness subtest of the Test of Attentional Performance may offer an objective method of evaluating self-reported fatigue, and may therefore - in addition to the Fatigue Severity Scale - be a suitable tool for the assessment of multiple sclerosis patients complaining of fatigue.