Sustained attention during prolonged walking in persons with multiple sclerosis

Abstract

Introduction: Walking is a cognitively demanding activity, as has been shown in long-distance assessments. It is known that there is often a decrease in walking speed during long-distance walking in persons with multiple sclerosis (pwMS) which could be related to reduced sustained attention while performing simultaneously performing a prolonged motor task (i.e., long distance walking task). Objective: This study investigated sustained attention during prolonged walking in pwMS withdifferent levels of disabilityand compared it with healthy controls (HC). Methods: Thirty pwMS with mild disability (EDSS<4.0), 16 pwMS with moderate to severe disability (EDSS 4.0-6.5), and 27 age-gender matched HC performed the 6-Minute Walk Test (6MWT) with an auditory vigilance task. Participants were auditory provided a letter every 2.5s through a headphone and were instructed to say "yes" as fast as possible when they heard one of two selected letters (L and R) and asked to not respond on other letters to assess vigilance. The number of errors and average reaction time in the vigilance task, and distance walked per minute were measured. Distance Walked Index (DWI; change in walking distance between min 1 and min 6) was calculated to determine walking fatigability. Repeated measures ANOVAs (RMANOVAs) were conducted on each outcome variable with post-hoc corrections. Results: Significant group * time interaction effects were found for reaction times.Reaction times significantly increased in persons with mild disability and moderate to severe disability groups, with greater increase in pwMS with moderate to severe disability (13.22%). There was no change in reaction time between min 1 to min 6 in HCs. Significant time effects were found for walking distance and number of errors, but there was no group*time interaction. The DWI was not different between mildly disabled pwMS and HC (-10.22% vs.-6.54%), but those with moderate to severe disability showed a significantly greater change (-20.59%) than mildly disabled pwMS. Conclusion: Our findings showed that attention and walking speed deteriorated over time during the six minutes of walking, especially in pwMS with higher disabilities. Change in sustained attention may explain the decrease in walking speed, and it should be further examined.