Ulrik Dalgas

Background: People with progressive multiple sclerosis (PMS) present motor (eg, walking) and cognitive impairments, and report fatigue. Fatigue encompasses fatigability which is objectively measured by the capacity to sustain a motor or cognitive task. Objective: To investigate the prevalence of walking and cognitive fatigability (CF) and the associated clinical characteristics in a large sample of PMS patients. Methods: PMS patients (25-65 years old) were included from 11 sites (Europe and North America), having cognitive impairment (1.28 standard deviation below normative data for the symbol digit modality test [SDMT]). Walking fatigability (WF) was assessed using the distance walk index (DWI) and CF using the SDMT (scores from the last 30 seconds compared to the first 30 seconds). Additional measures were: cognitive assessment—Brief International Cognitive Assessment for multiple sclerosis (MS), cardiorespiratory fitness, 6-minute walk, physical activity, depressive symptoms, perceived fatigue—Modified Fatigue Impact Scale (MFIS), MS impact—MSIS-29, and walking ability. Results: Of 298 participants, 153 (51%) presented WF (DWI = −28.9 ± 22.1%) and 196 (66%) presented CF (−29.7 ± 15%). Clinical characteristics (EDSS, disease duration, and use of assistive device) were worse in patients with versus without WF. They also presented worse scores on MSIS-29 physical, MFIS total and physical and reduced physical capacity. CF patients scored better in the MSIS-29 physical and MFIS psychosocial, compared to non-CF group. Magnitude of CF and WF were not related. Conclusions: Half of the cognitively-impaired PMS population presented WF which was associated with higher disability, physical functions, and fatigue. There was a high prevalence of CF but without strong associations with clinical, cognitive, and physical functions. Trial Registration Number: The “CogEx-study,” www.clinicaltrial.gov identifier number: NCT03679468.