Depression meditated 53% of the fatigue-mental quality of life relationship.
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Depression mediation was strongest for the role limitations and emotional wellbeing subdomains.
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Physical activity mediated little of the fatigue-mental quality of life relationship.
Abstract
Background
Fatigue is among the most prevalent symptoms for people with multiple sclerosis (pwMS) and is significantly detrimental to mental health-related (mental) quality of life (QoL). We examined the role of depression and physical activity as mediators in the fatigue-QoL relationship in pwMS.
Methods
Using baseline cross-sectional data from an international cohort of 2,104 pwMS, characteristics of fatigue and mental QoL, measured by Fatigue Severity Scale and MSQOL-54 respectively, were assessed using linear and log-binomial regression. Structural Equation Models (SEM) were used to explore the mediating roles of depression and physical activity between fatigue and mental QoL.
Results
The median mental QoL score was 71.9/100. The mean fatigue score was 41.5/63, with 65.6% participants having clinically significant fatigue. In the SEM evaluating depression as a mediator of the fatigue-QoL relationship, mental QoL was 14.72 points lower (95% CI: -16.43 -13.01, p<0.001) in participants with clinically significant fatigue, of which depression accounted for 53.0% (-7.80, 95% CI: -9.03 -6.57, p<0.001). In the SEM evaluating physical activity as a mediator of the fatigue-QoL relationship, mental QoL was 10.89 points lower (95% CI: -12.47, -9.32, p<0.001) in participants with clinically significant fatigue, of which the indirect effect via physical activity accounted for only 4.4% (-0.48, 95% CI: -0.81, -0.14, p=0.005).
Conclusion
Depression accounted for the majority of the fatigue-mental QoL relationship when modelled as a mediator, while physical activity had only a minor role. Our findings may inform the development of treatments for reducing the impacts of fatigue and improving mental QoL in pwMS.