The Relationship Between Fatigue and Lower Extremity Function in People with Multiple Sclerosis with the Absence of Clinical Disability

INTRODUCTION: Impairment in the lower extremity function and mobility is a symptom often among people with multiple sclerosis (pwMS), even in the absence of clinical disability. Fatigue is one of the most common symptoms reported by at least 80% of pwMS during any disease. This study investigated the relationship between fatigue and lower extremity function, which is assessed by the Six Spot Step test (SSST) in pwMS with the absence of clinical disability.
METHODS: A total of 477 pwMS with an Expanded Disability Status scale (EDSS) score of ≤1.5 were included in the study. The SSST was used to evaluate the complex sensorimotor function of lower extremity function, such as lower extremity muscle strength, coordination, and balance. Participants with SSST performance above 8 seconds were classified as impaired. In addition, a Modified Fatigue Impact scale-5- item version was used to evaluate perceived fatigue. Demographic (gender, age) and clinical data (disability level and disease duration) of the participants were obtained from interviews and medical records.
RESULTS: Impairment in SSST performance was detected in 171 (35.85%) pwMS. Univariate regression analysis revealed that fatigue was significantly associated with the SSST (p<0.001). Furthermore, fatigue was still an associated factor in the multivariate regression analysis after adjusting for age, gender, and disability level (p<0.001).
DISCUSSION AND CONCLUSION: This study showed that even in the absence of disability, fatigue could be related to impairment in SSST performance. Considering the reflection of SSST performance on functional mobility, ambulation, and daily life in pwMS, it is essential to include the fatigue in the evaluation and treatment of pwMS with the absence of clinical disability.