Baseline comorbidity levels in biologic and standard DMARD treated patients with rheumatoid arthritis: results from a national patient register

Objective: To describe the occurrence of baseline comorbidity in subjects with active rheumatoid arthritis starting treatment with biological agents. Such data are necessary to interpret the reported occurrence of adverse events following treatment. Methods: Baseline comorbidity was recorded in a large national cohort of patients with rheumatoid arthritis newly starting biological agents. The distribution of the number and types of comorbidities is presented. Results: In all, 7818 patients treated with biological agents (infliximab 3332, etanercept 3302, adalimumab 1059, anakinra 132) were included in the analysis. Comorbidity was common, with 58% of patients having at least one comorbid condition and 25% having more than one. The most frequent comorbid conditions were hypertension, depression, peptic ulcer disease, and respiratory disease. Conclusions: In routine use, patients treated with biological agents have high levels of baseline comorbidity, which should influence the interpretation of reported adverse events.