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

Abstract

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.

Figure 1. Path analysis model of predictors of health-related quality of life (HRQoL) in multiple sclerosis (MS)

The value on the double-headed arrow is a correlation coefficient; values on single-headed arrows are standardized regression coefficients; the value to the upper right of the dependent variable is the squared multiple correlation. CFI = Comparative Fit Index; CI = confidence interval; DFIS = Daily Fatigue Impact Scale; EDSS = Expanded Disability Status Scale; HADS-A = Hospital Anxiety and Depression Scale anxiety subscale; HADS-D = Hospital Anxiety and Depression Scale depression subscale; HUI = Health Utilities Index; RMSEA = root mean square error of approximation.

Figure 2. Recruitment process and flow of participants in multiple sclerosis (MS) clinics

*Patients seen multiple times (e.g., for relapse visits or clinical trials) within the recruitment period were only counted once. **Recruiter missed participants in the clinic. Thus, participation rate = 949/(1,144–5) = 82.6%.