Health-related quality of life in multiple sclerosis: Direct and indirect effects of comorbidity

Objective: To evaluate the direct and indirect influences of physical comorbidity, symptoms of depression and anxiety, fatigue, and disability on health-related quality of life (HRQoL) in persons with multiple sclerosis (MS). Methods: A large (n = 949) sample of adults with MS was recruited from 4 Canadian MS clinics. HRQoL was assessed using the patient-reported Health Utilities Index Mark 3. Expanded Disability Status Scale scores, physical comorbidity, depression, anxiety, and fatigue were evaluated as predictors of HRQoL in a cross-sectional path analysis. Results: All predictors were significantly associated with HRQoL and together accounted for a large proportion of variance (63%). Overall, disability status most strongly affected HRQoL (β = −0.52) but it was closely followed by depressive symptoms (β = −0.50). The direct associations of physical comorbidity and anxiety with HRQoL were small (β = −0.08 and −0.10, respectively), but these associations were stronger when indirect effects through other variables (depression, fatigue) were also considered (physical comorbidity: β = −0.20; anxiety: β = −0.34). Conclusions: Increased disability, depression and anxiety symptoms, fatigue, and physical comorbidity are associated with decreased HRQoL in MS. Disability most strongly diminishes HRQoL and, thus, interventions that reduce disability are expected to yield the most substantial improvement in HRQoL. Yet, interventions targeting other factors amenable to change, particularly depression but also anxiety, fatigue, and physical comorbidities, may all result in meaningful improvements in HRQoL, as well. Our findings point to the importance of further research confirming the efficacy of such interventions.