Relationship between perceived fatigue and performance fatigability in people with multiple sclerosis: A systematic review and meta-analysis

Abstract

Background: Perceived fatigue (i.e., subjective perception of reduced capacity) is one of the most common and disabling symptoms for people with multiple sclerosis (MS). Perceived fatigue may also be related to performance fatigability (i.e., decline in physical performance over time), although study findings have been inconsistent.

Objective: To locate all studies reporting the relationship between perceived fatigue and fatigability in people with MS, determine the population correlation, and examine moderating variables of the correlation size.

Methods: In accordance with PRISMA guidelines, systematic searches were completed in Medline, PsychInfo, Google Scholar, and the Cochrane Library for peer-reviewed articles published between March 1983 and August 2016. Included articles measured perceived fatigue and performance fatigability in people with MS and provided a correlation between measures. Moderator variables expected to influence the relationship were also coded. Searches located 19 studies of 848 people with MS and a random-effects model was used to pool correlations.

Results: The mean correlation between fatigue and fatigability was positive, "medium" in magnitude, and statistically significant, r=0.31 (95% CI=0.21, 0.42), p<0.001. Despite moderate between-study heterogeneity (I²=46%) no statistically significant moderators were found, perhaps due to the small number of studies per moderator category.

Conclusion: There is a significant relationship between perceived fatigue and fatigability in MS, such that people reporting elevated fatigue also are highly fatigable. The size of the relationship is not large enough to suggest fatigue and fatigability are the same construct, and both should continue to be assessed independently.

Keywords: Contraction; Energy; Exercise; Perception; Symptom; Tired.

Figure 1

Study selection flow diagram.

Figure 2

Forest plot of effect sizes. Negative values indicate an inverse relationship between perceived fatigue and fatigability, while positive values indicate a direct relationship. The author name on the left indicates the corresponding study with the corresponding correlation and 95% confidence interval across on the right. The dot pictorially represents the correlation, the size of the dot indicates weight, and the horizontal line shows the confidence interval. The dashed line indicates the mean correlation.

Figure 3

Funnel plot of effect sizes. Each correlation is on the x-axis and standard error is on the y-axis. In the absence of publication bias a funnel shape is created by the spread of effect sizes.