Incidence and prevalence of seropositive rheumatoid arthritis among Korean women of childbearing age: a nationwide population-based study

Background/Aims: Women with rheumatoid arthritis (RA) are often diagnosed with the disease during their reproductive years; however, its incidence and prevalence among women of childbearing age have not been studied. The objective of this study was to estimate the incidence and prevalence of seropositive rheumatoid arthritis (SPRA) among Korean women of childbearing age. Methods: Women aged 20 to 44 years with SPRA were identified from National Health Insurance Service-National Health Information Database (2009 to 2016). SPRA was defined by International Classification of Diseases, 10th revision code, M05. Incidence and prevalence were calculated per 100,000 person-years and stratified by year and age. Results: The average incidence and prevalence of SPRA from 2011 to 2016 among women of childbearing age was 24.1/100,000 person-years (95% confidence interval [CI], 23.7 to 24.5) and 105.2/100,000 person-years (95% CI, 100.9 to 109.5), respectively. The incidence increased annually from 21.0/100,000 person-years (95% CI, 20.1 to 21.9) in 2009 to 28.4 person-years (95% CI, 27.3 to 29.5) in 2016. Similarly, the prevalence increased annually from 95.7/100,000 person-years (95% CI, 93.7 to 97.6) in 2009 to 111.0 person-years (95% CI, 108.9 to 113.2) in 2015, with a slight decrease in 2016 (110.4 person-years; 95% CI, 108.2 to 112.6). The incidence and prevalence of SPRA increased with advancing age. The peak age for both incidence and prevalence of SPRA among women of childbearing age was 40 to 44 years. Conclusions: The risk of SPRA is high in women during their childbearing years; this population bears a significant disease burden. This calls for special attention to this particular population group to reduce the risk and burden of this disease.