Relationship Between Fatigability and Perceived Fatigue Measured Using the Neurological Fatigue Index in People with Multiple Sclerosis.

Abstract

Understanding the relationship between perceived fatigue and performance fatigability could lead to more effective interventions to manage multiple sclerosis (MS)-related fatigue. However, the relationship between self-perceived fatigue measured using the Neurological Fatigue Index (NFI-MS) and performance fatigability in people with MS is unknown. We sought to explore the relationship between the NFI-MS and performance fatigability in people with MS. Fifty-two participants (mean ± SD age, 46.8 ± 10.1 years) completed the study. Three measures of performance fatigability were used: percent change in meters walked from first to last minute of the 6-Minute Walk Test, percent change in force exerted from first to last trial on a repetitive maximal hand grip test, and response speed variability on the Continuous Performance Test. Perceived physical and cognitive fatigue were measured using the NFI-MS. The state level of fatigue was examined immediately before and after performing the fatigability measures using a one-item visual analogue fatigue scale. Of the three performance fatigability measures, only the attentional task (response speed variability) was significantly associated with NFI-MS physical (r = 0.326, P = .020) and cognitive (r = 0.276, P = .050) domain scores. Participants demonstrated significantly higher state levels of fatigue after performing all performance fatigability measures (P ≤ .001). The NFI-MS and the performance fatigability measures used in this study are easy to administer. We encourage wider use of these measures in clinical and research settings for comprehensive assessment of MS-related fatigue.