Pos0004 Trend in the Incidence of Rheumatoid Arthritis in Korea for 11-Years (2006-2017)

Background: Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, characterized by joint damage. It occurs in approximately 0.3-1.0% of the worldwide population, with an annual incidence rate of 10-20 per 100,000 individuals. However, no incidence analyses have been conducted on Koreans beyond the year 2013. Objectives: This study aimed to calculate the incidence of rheumatoid arthritis and examine its trends using whole Korean NHIS claims data from 2007 to 2017. Methods: We used 16 years of Korean NHIS claims data from 01 January 2002 to 31 December 2017. Data from 2002 to 2006 (5years) were used as a washout period to define newly diagnosed RA patients. Patients were defined diagnostic RA who were diagnosed with ICD-10 code (M05 and M06). Those who had only diagnostic code without prescribed RA drugs (DMARDs) were excluded from the prevalent RA patients. we set the 5-year period prior to 2006 as a disease-free period. Results: From 2007 to 2017, the incidence rate of RA was 35 to 43 per 100,000 individuals (Figure 1(a)). The female-to-male ratio was approximately 3 to 3.5 (Figure 1(b)). Notably, the sex-standardized incidence rate was highest in the 60-69 age group, but it gradually declined, resulting in a reversal in 2017, with the highest incidence rate observed in the 50-59 age group (50-59 age group of 78.7/100,000, 60-69 age group of 76.8/100,000) (Figure 1(c)). Moreover, the incidence of elderly-onset RA (EORA) in individuals aged over 60 exhibited a decreasing trend during the study period (60-69 age group of -6.45, 95% CI=-8.27 to -4.62, p<0.001, ≥70 age group of -6.09, 95% CI=-7.66 to -4.53, p<0.001) (Table 1). Conclusion: This study is the first to analyze the incidence trend RA over an 11-year period. There were notable changes in age-specific incidence rates. The incidence rate in the 60-69 age group gradually decreased, resulting in the highest incidence rate observed in the 50-59 age group in 2017. Additionally, there was a decreasing trend in the incidence of elderly-onset RA (EORA). REFERENCES: [1] Kim H, Sung Y-K. Epidemiology of rheumatoid arthritis in Korea. Journal of Rheumatic Diseases. 2021;28(2):60-7. [2] Sung Y-K, Cho S-K, Choi C-B, Bae S-C. Prevalence and incidence of rheumatoid arthritis in South Korea. Rheumatology international. 2013;33:1525-32. [3] Sung Y-K, Cho S-K, Choi C-B, Park S-Y, Shim J, Ahn JK, et al., editors. Korean Observational Study Network for Arthritis (KORONA): establishment of a prospective multicenter cohort for rheumatoid arthritis in South Korea. Seminars in arthritis and rheumatism; 2012: Elsevier. Acknowledgements: NIL. Disclosure of Interests: None declared.