Subjective cognitive fatigue in multiple sclerosis depends on task length.

Joshua Sandry,Helen M Genova,Ekaterina Dobryakova,Glenn Wylie,John Deluca

doi:10.3389/fneur.2014.00214

Abstract

Objective: The objective of this paper is to investigate the interrelationship between subjective and objective cognitive fatigue, information processing domain [processing speed (PS) vs. working memory (WM)], cognitive load (high vs. low), and time on task in Multiple Sclerosis (MS).Methods: Thirty-two MS participants and 24 healthy controls completed experimental tasks in both the PS and WM domains with different levels of cognitive load. Subjective cognitive fatigue was measured using a visual analog scale at baseline and at multiple time points throughout the experiment.Results: A mixed model ANOVA revealed that subjective cognitive fatigue was higher for the PS task, increased across time, and was higher in the MS group. These findings were qualified by an interaction demonstrating that the MS group showed a steeper increase in subjective cognitive fatigue over time than the healthy control group. Subjective and objective (i.e., performance) cognitive fatigue were not correlated.Conclusion: In this study, subjective and objective cognitive fatigue appears to be independent and cognitive fatigue does not depend on cognitive load. Subjective cognitive fatigue increased with time on task and subjective cognitive fatigue increased more steeply for the MS group. These data suggest that cognitive fatigue in MS is a function of time, that is, the longer participants were engaged in a cognitive task, the more likely it was for them to report increases in cognitive fatigue.

Highlights

Fatigue is perhaps the most common complaint associated with Multiple Sclerosis (MS) [1] with prevalence estimates ranging between 70 and 90% [2,3,4]
Subjective cognitive fatigue increased with time on task and subjective cognitive fatigue increased more steeply for the MS group
These data suggest that cognitive fatigue in MS is a function of time, that is, the longer participants were engaged in a cognitive task, the more likely it was for them to report increases in cognitive fatigue

Summary

Introduction

Fatigue is perhaps the most common complaint associated with Multiple Sclerosis (MS) [1] with prevalence estimates ranging between 70 and 90% [2,3,4]. Fatigue can be cognitive or motoric and originate at a central level (i.e., the central nervous system) or peripheral level (i.e., peripheral nerve and muscle) [5]. Cognitive fatigue may manifest as subjective sensations or objective changes in performance, fatigue, and fatigability, respectively [7]. Treating cognitive fatigue clinically remains difficult, because a basic understanding of the variables that contribute to cognitive fatigue are not well defined. The present paper investigates the task parameters that lead to cognitive fatigue in MS. This knowledge may help to inform future research as well as clinical evaluations of cognitive fatigue in MS. Novel insights into how and why cognitive fatigue manifests may lead to improved clinical treatment strategies for cognitive fatigue

Methods

Results

Discussion

Conclusion