Medical care costs of patients with rheumatoid arthritis during the prebiologics period in Japan: a large prospective observational cohort study

Our objective was to describe outpatient medical care costs of patients with rheumatoid arthritis (RA) in the prebiologics period in Japan. The outpatient costs of 6,771 RA patients (17,666 patient years) who were enrolled in an observational cohort study at the Institute of Rheumatology, Rheumatoid Arthritis (IORRA), in Tokyo, Japan, were calculated from the billing records dated from 2000 to 2004. Associations between outpatient costs and variables such as age, RA duration, RA disease activities, and disability levels were assessed. The average outpatient cost gradually increased (+7.7% in 4 years) from 271,498 JPY per year in 2000 to 292,417 JPY per year in 2004. Medications accounted for approximately 50% of total outpatient costs, which increased 29.6% during the 4 years. The outpatient costs increased in association with aging, longer RA duration, higher Disease Activity Score of 28 Joints (DAS28), and higher Japanese version of Health Assessment Questionnaire (J-HAQ) score. Generalized linear regression analysis revealed that both DAS28 and J-HAQ scores were the most significant factors associated with outpatient costs (p < 0.001). Outpatient costs for patients with RA increased year after year over the 4-year period under observation in Japan. Medical costs were higher with increasing RA disease activity and disability levels.