Epidemiological characteristics of rheumatoid arthritis in Japan: Prevalence estimates using a nationwide...

Objectives: To elucidate the epidemiological characteristics of patients with rheumatoid arthritis (RA) in Japan using data from the Comprehensive Survey of Living Conditions, a nationwide questionnaire survey conducted in 2016.Methods: In total, 222,365 men and 245,251 women aged ≥16 years were included in the study. RA patients were defined as those who reported 'currently receiving treatment for RA at hospitals, clinics, or a facility for Japanese traditional massage, acupuncture, moxibustion, or judo-orthopedics.' The number of RA patients was estimated from the age-specific prevalence and total Japanese population in 2016. Further, the prevalence of individuals experiencing difficulties in activities of daily living due to health problems and those with mental distress as evaluated by K6 Scale was examined.Results: The estimated number and prevalence of RA in Japan with 95% confidence interval was 822 (768-880) thousand and 0.75% (0.70-0.80%). The population peaked in the late 60s, and the prevalence continued increasing until the early 80s, regardless of sex. Compared with non-RA participants, RA patients were more likely to experience difficulties in activities and to be distressed.Conclusion: High prevalence of RA in older age and mental and physical burden among RA patients were confirmed.