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

Mayis Aldughmi, PT; Jared Bruce, PhD; Catherine F. Siengsukon, PT, PhD

Correspondence: Catherine F. Siengsukon, PT, PhD, University of Kansas Medical Center, 3901 Rainbow Blvd., Mail Stop 2002, Kansas City, KS 66160; e-mail: csiengsukon@kumc.edu.

Background: 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. Therefore, the aim of the study was to explore the relationship between the NFI-MS and performance fatigability in people with MS.

Methods: Fifty-two participants (mean age: 46.8 ± 10.1) completed the study. Three measures of performance fatigability were utilized: percent change in meters walked from the first to last minute of the 6-Minute Walk Test (6MWT), percent change in force exerted from the first to last trial on a repetitive maximal hand grip test, and Response Speed Variability (RSV) on the Continuous Performance Test (CPT). 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 1-item Visual Analogue Fatigue Scale (VAFS).

Results: Out of the three performance fatigability measures, only the attentional task (RSV) was significantly associated with the NFI-MS physical domain (r = .326, P = .020) and NFI-MS cognitive domain (r = .276, P = .05). Participants demonstrated significantly higher state levels fatigue after performing all the performance fatigability measures (P ≤ .001).

Conclusions: The NFI-MS and the performance fatigability measures utilized in this study are easy to administer. We encourage a wider use of those measures in clinical and research settings for a comprehensive assessment of MS-related fatigue.