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.