Geographic variations in rheumatoid arthritis treatment in Japan: A nationwide retrospective study using the national database of health insurance claims and specific health checkups of Japan

Objectives To characterize the treatments for rheumatoid arthritis (RA) among institution types and prefectures in Japan. Methods Using the National Database of Health Insurance Claims and Specific Health Checkups of Japan in the 2017 fiscal year, we investigated disease-modifying antirheumatic drug (DMARD) and oral corticosteroid prescription trends across 825 thousand RA patients. These data were compared between specialized and non-specialized institutions and by prefecture. RA specialized institutions (SIs) were defined as either institutions registered in the rheumatology training program at the Japan College of Rheumatology or institutions where board-certified rheumatologists were employed. Results The overall percentage of patients who never visited an SI was 31.8% and increased with age (16-29 years old = 15.6%; >= 80 years = 42.8%). In twelve prefectures (25.5%), the proportions of patients who never visited an SI were at least 10% higher than the overall average. The proportions of patients who only visited SIs and were prescribed methotrexate and biological DMARDs were ranged from 51.9-72.9% and 19.5-33.2%, respectively. However, those of patients who had never visited an SI and were prescribed those medications were 44.0-71.6% and 7.2-28.0%, respectively. Conclusions This is the first study evaluating the trends in RA treatments by prefecture and institution specialty by using the NDB Japan. Opportunities of patients with RA for visiting SI was unevenly distributed in Japan, affecting some aspects of treatment provided.