Is the impact of fatigue related to walking capacity and perceived ability in persons with multiple sclerosis? A multicenter study

Background: The relationship between fatigue impact and walking capacity and perceived ability in patients with multiple sclerosis (MS) is inconclusive in the existing literature. A better understanding might guide new treatment avenues for fatigue and/or walking capacity in patients with MS. Objective: To investigate the relationship between the subjective impact of fatigue and objective walking capacity as well as subjective walking ability in MS patients. Methods: A cross-sectional multicenter study design was applied. Ambulatory MS patients (n = 189, age: 47.6 10.5 years; gender: 115/74 women/men; Expanded Disability Status Scale (EDSS): 4.1 1.8 [range: 0-6.5]) were tested at 11 sites. Objective tests of walking capacity included short walking tests (Timed 25-Foot Walk (T25FW), 10-Metre Walk Test (10mVVT) at usual and fastest speed and the timed up and go (TUG)), and long walking tests (2- and 6-Minute Walk Tests (MWT). Subjective walking ability was tested applying the Multiple Sclerosis Walking Scale-12 (MSWS-12). Fatigue impact was measured by the self-reported modified fatigue impact scale (MFIS) consisting of a total score (MFIStotni) and three subscales (MFISphysic i, MFIS,g itive and MFISpsythusuco). Uni- and multivariate regression analysis were performed to evaluate the relation between walking and fatigue impact. Results: MFIStotal was negatively related with long (6MWT, r = 0.14, p = 0.05) and short composite (TUG, r = 0.22, p = 0.003) walking measures. MFISphysii showed a significant albeit weak relationship to walking speed in all walking capacity tests (r = 0.22 to 0.33, p <.0001), which persisted in the multivariate linear regression analysis. Subjective walking ability (MSWS-12) was related to MFIStutai (r = 0.49, p < 0.0001), as well as to all other subscales of MFIS (r = 0.24-0.63, p < 0.001), showing stronger relationships than objective measures of walking. Conclusions: The physical impact of fatigue is weakly related to objective walking capacity, while general, physical, cognitive and psychosocial fatigue impact are weakly to moderately related to subjective walking ability, when analysed in a large heterogeneous sample of MS patients.