Multimorbidity and Fatigue in Rheumatoid Arthritis: A Cross-Sectional Study of a Population-Based Cohort

Introduction: The objective was to evaluate the relationships between multimorbidity and overall fatigue as well as fatigue subdomains in patients with rheumatoid arthritis (RA). Methods: A cross-sectional study of a population-based cohort of patients with RA was performed. Fatigue was assessed using the Bristol Rheumatoid Arthritis Fatigue Multidimensional Questionnaire (BRAF-MDQ). Patients’ medical records were reviewed for 25 chronic comorbidities prior to the BRAF-MDQ. Linear and logistic regression models were used to estimate the differences in BRAF-MDQ total and subdomain (physical, living, cognitive, and emotional) scores associated with multimorbidity, adjusting for age, sex, disease duration, obesity, smoking, C-reactive protein, and RA autoantibodies. Higher BRAF-MDQ scores indicate greater fatigue severity. Results: The cohort included 192 patients, median age 62 years, and median RA duration 13 years. Multimorbidity was common with 93 (48%) having ≥ 2 comorbidities, and 27 (14%) having ≥ 4 comorbidities. The median BRAF-MDQ total score was 9 (interquartile range 3–18), with higher scores indicating greater fatigue. Patients with ≥ 4 comorbidities had higher total BRAF-MDQ scores (median 16.5, interquartile range: 6.8–24.8) than patients with < 4 comorbidities (7.5, 2.8–16.0; p = 0.014). Each additional comorbidity was associated with a 2.33 (95% confidence interval [CI] 1.10–3.56) unit increase in total BRAF-MDQ score (p < 0.001), and the presence of ≥ 4 comorbidities was associated with a 9.33 (95% CI 3.92–14.7) unit increase in total BRAF-MDQ score. Multimorbidity was significantly associated with all four fatigue subdomains in adjusted models. Conclusions: Multimorbidity is associated with increased fatigue in patients with RA. The findings suggest that interventions targeting multimorbidity could help alleviate treatment-refractory fatigue in patients with RA and other rheumatic diseases.