Walking fatigability in multiple sclerosis: A comparison between the 2- and the 6-minute walk test and an evaluation of associated factors

Abstract

Walking disorders are common in patients with multiple sclerosis (MS). Among these, walking fatigability is a common complaint of patients, but it needs to be better characterized. This work aims to compare the fatigability induced by a 2, and a 6- minute walk test (2MWT; 6MWT) and to investigate the factors associated with it. Twenty-seven MS patients (divided into subgroups according to disease severity [EDSS 3–4 and 4.5–6.5]) and 9 control subjects were included in this interventional, prospective and single-center study. The subjects realized a 2-minute walk test (2MWT) then a 6-minute walk test (6MWT) during which were assessed the walking fatigability, energy spending and the rate of perceived exertion (RPE, Borg scale). In addition, other operating parameters (25-foot walk test (T25FW), spatial and temporal parameters, self-evaluation of walking ability (MSWS-12)) and major deficiencies leading to walking troubles (paresis, spasticity…) were evaluated. Walking fatigability was present in the MS group, but with different characteristics depending on the severity of the disease. In the high EDSS group, it was present at the 2MWT and 6MWT ( p = 0.001) and correlated between the two tests. In the lower EDSS group as in controls, fatigability was objectified only in the 6MWT ( p < 0.001 and p < 0.01 respectively). The deceleration index seems to be the simplest and most sensitive assessment of walking fatigability. The factors associated with fatigue in the 6MWT (univariate analysis) were the EDSS score ( p < 0.05), the pyramidal function ( r = –0.67; p < 0,001) but not the spasticity or sensory or cerebellar functions, gait speed ( r = 0.60; p < 0,01) and cadence ( r = 0.69; p < 0.001), posturographic data ( r = –0.54; p < 0.01) and RPE ( r = –0.6; p ≤ 0.001). The links between fatigue and the energy cost of walking were more contrasted. The method of assessment of walking fatigability should be considered depending on the severity of the disease. Among the various tools, the deceleration index seems most sensible and simple to use. Factors associated with walking fatigability are yet to be more precisely determined.