Association of Comorbidities in Spondyloarthritis With Poor Function, Work Disability, and Quality of Life: Results From the Assessment of SpondyloArthritis International Society Comorbidities in Spondyloarthritis Study

Objective. Comorbidities add to the burden of disease and its complexity, and may prevent the achievement of treat-to-target goals. The objective of this study was to study the relationship between comorbidities and key disease outcomes in spondyloarthritis (SpA), namely function, work ability, and quality of life. Methods. Patients from the multinational (22 countries), cross-sectional Assessment in SpondyloArthritis international Society (ASAS) Comorbidities in Spondyloarthritis study were included in the analysis, provided they fulfilled the ASAS criteria. Data on comorbidities based on both self- and physician-report were collected through questionnaires and were subsequently used to compute the Rheumatic Disease Comorbidity Index (RDCI). Univariable and multivariable (adjusted for relevant confounders) multilevel (with country as a random effect) linear or logistic (as appropriate) regression analyses were conducted to investigate the relationship between the RDCI and functional ability, work ability, and quality of life. Results. In total, 3,370 of 3,984 recruited patients (85%) fulfilled the ASAS criteria: 66% were male, mean +/- SD age was 43 +/- 14 years, mean +/- SD disease duration was 8.4 +/- 9.5 years, and mean +/- SD RDCI was 0.7 +/- 1.1. At least 1 comorbidity was reported in 51% of patients; 9% had >= 3 comorbidities. RDCI was independently associated with a higher Bath Ankylosing Spondylitis Functional Index score (beta = 0.37, 95% confidence interval [95% CI] 0.30, 0.43), lower EuroQol 5-domain questionnaire (beta = -0.03, 95% CI -0.04, 0.02), less work employment (odds ratio [OR] 0.83, 95% CI 0.76, 0.91), higher absenteeism (OR 1.18, 95% CI 1.04, 1.34), and higher presenteeism (OR 1.42, 95% CI 1.26, 1.61). Conclusion. Comorbidities in SpA adversely influence physical function, work ability, and quality of life and are important to take into account in daily clinical practice.