Background: Multiple sclerosis (MS) patients suffer very often from MS fatigue and sleep problems. Despite the detrimental impact on the activities of daily living, a short and objective quantification of fatigue and sleep problems is currently lacking.
Objective: The objective of the study was to systematically investigate tonic, intrinsic, and phasic alertness and the relationship of these performance-based measures with self-report measures of fatigue and quality of sleep.
Methods: Thirty-three MS patients without (MS-) and 26 with selected comorbid disorders (MS+) and 43 healthy controls (HCs) performed the pupillographic sleepiness test (measuring tonic alertness) and the alertness subtest of the Test of Attentional Performance (measuring intrinsic and phasic alertness).
Results: Self-reported and performance-based measures revealed poorer performance for both MS groups compared to HC. MS+ patients presented higher rates of MS fatigue, sleep problems and depressive symptoms but similar alertness scores compared to MS- patients. However, tonic alertness was only higher in MS- patients compared to HC. Intrinsic and phasic alertness correlated moderately with fatigue ratings.
Conclusion: In the diagnostic process of MS fatigue and quality of sleep comorbid disorders (depression, anemia, thyroid dysfunction) and performance-based measures such as alertness should be considered in daily clinical practice.
Keywords: multiple sclerosis; multiple sclerosis-related fatigue; pupillographic sleepiness test; sleep; tonic/intrinsic/phasic alertness.