Fatigue Measured Using the Neurological Fatigue Index Is Associated with Poor Sleep Quality and Inattentiveness in People with Multiple Sclerosis
Objectives: The purpose of this study was to examine the relationship between fatigue measured using the Neurological Fatigue Index (NFI-MS) and sleep quality and sustained attention.
Subjects:Fifty-two individuals with relapsing-remitting or secondary-progressive MS (46.8 ± 10.1 years of age) participated in this study.
Methods: Participants completed the NFI-MS that assess fatigue in the past two weeks, the Pittsburgh Sleep Quality Index (PSQI) global score to assess sleep quality in the past month, and the Continuous Performance Test (CPT) to assess sustained attention. The NFI-MS has two sleep components that assess how sleep quality contributes to fatigue (relief by diurnal sleep and abnormal nocturnal sleep), as well as a physical and cognitive components. Spearman’s correlations were utilized to examine the associations between the outcome measures of interest.
Results: There was a significant positive association between the NFI-MS abnormal nocturnal sleep component and the PSQI global score (r= .571, p= < .001), meaning higher fatigue attributed to abnormal sleep is associated with poorer sleep quality. There was a significant positive association between the NFI-MS cognitive component and the CPT measure of response speed (r= .339, p= 0.014), meaning that higher cognitive fatigue is associated with a slower reaction to the target.
Conclusions: Cognitive fatigue is associated with decreased sustained attention. This is clinically important as sustained attention is necessary for individuals to effectively perform continuous and repetitive activities, and being cognitively fatigued may affect the performance of these tasks. The finding that fatigue is associated with poor sleep quality emphasizes the need for health care providers to consider the assessment of sleep quality and possibly address sleep disturbances as part of the treatment plan.