To estimate the prevalence and age-stratified treatment trends and clinical characteristics of rheumatoid arthritis (RA) in Japan.
Using 7 RA definitions, the prevalence of RA in those aged ≥16 years was estimated using the National Database of Health Insurance Claims and Specific Health Checkups of Japan in the fiscal year 2017. We analyzed age-stratified trends in characteristics and treatments.
Of 1 116 122 patients aged ≥16 years with at least 1 RA-related International Classification of Diseases-10 code, 825.7 thousand patients (women, 76.3%) were assessed as having RA with an estimated prevalence of 0.65%. The highest age-stratified prevalence was 1.63% in patients aged 70-79 years. Overall, 60.8% and 7.0% of patients with RA were aged ≥65 years and ≥85 years, respectively. Methotrexate use was most frequent in patients aged 50-59 years (73.0%) and least frequent in patients aged ≥85 years (38.2%). Biologic disease-modifying antirheumatic drugs use was 50.9% in patients aged 16-19 years and decreased to 13.7% in those aged ≥85 years. Preference for the use of tumor necrosis factor inhibitors versus abatacept decreased from 24.0:1 to 1.7:1 in patients aged 16-19 years and ≥85 years, respectively. The prevalence of cardiovascular disease was 3.5% in patients aged 60-69 years and 12.1% in those aged ≥85 years. Overall RA-related orthopedic surgeries were most prevalent in patients aged 70-79 years.
The estimated prevalence of patients with RA in Japan was 0.65%. Age-stratified treatment trends and clinical characteristics have been described in a super-aged society for the first time.