Impact of Comorbidity on Physical Function in Patients With Ankylosing Spondylitis and Psoriatic Arthritis Attending Rheumatology Clinics: Results From a Cross-Sectional Study

Objective To evaluate the impact of comorbidities on physical function in patients with ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Methods This was a cross-sectional analysis of the baseline visit from the Cardiovascular in Rheumatology study. Multivariate models with physical function as the dependent variable (Bath Ankylosing Spondylitis Functional Index and Health Assessment Questionnaire for AS and PsA, respectively) were performed. Independent variables were a proxy for the Charlson Comorbidity Index (CCIp; range 0-27), sociodemographic data, disease activity (erythrocyte sedimentation rate [ESR] and Bath Ankylosing Spondylitis Disease Activity Index [BASDAI] in AS; Disease Activity Score in 28 joints [DAS28] using the ESR in PsA), disease duration, radiographic damage, and treatments. Results were reported as beta coefficients, 95% confidence intervals (95% CIs), andPvalues. Results We included 738 patients with AS and 721 with PsA; 21% of patients had >1 comorbidity. Comorbidity burden (CCIp) was independently associated with worse adjusted physical function in patients with PsA (beta = 0.11). Also, female sex (beta = 0.14), disease duration (beta = 0.01), disease activity (DAS28-ESR; beta = 0.19), and the use of nonsteroidal antiinflammatory drugs (beta = 0.09), glucocorticoids (beta = 0.11), and biologics (beta = 0.15) were associated with worse function in patients with PsA. A higher education level was associated with less disability (beta = -0.14). In patients with AS, age (beta = 0.03), disease activity (BASDAI; beta = 0.81), radiographic damage (beta = 0.61), and the use of biologics (beta = 0.51) were independently associated with worse function on multivariate analyses, but CCIp was not. Conclusion The presence of comorbidities in patients with PsA is independently associated with worse physical function. The detection and control of the comorbidities may yield an integral management of the disease.