Incidence and prevalence of rheumatoid arthritis in Thailand based on National administrative health data and a comprehensive literature review.

Rheumatoid arthritis (RA) is an inflammatory arthritis that causes economic burden. Epidemiologic data may help to improve economic impact and the healthcare system. The incidence and prevalence of RA vary among the regions while there is no data about the incidence and limited data about the prevalence of RA in Thailand. We aim to estimate the incidence and prevalence of RA in Thailand between 2017 and 2020. The descriptive epidemiologic study was performed using the Information and Communication Technology Center, Ministry of Public Health covering all different healthcare providers during the study period. Demographic data from a primary diagnosis of M05: seropositive rheumatoid arthritis according to ICD 10 and over 18 years of age between 2017 and 2020 were reviewed. The incidence and prevalence of RA were analyzed with their 95% confidence interval (CI) from an overall national perspective and regionally. In 2020, there were 64,849 RA cases in Thailand out of a total population of 65,421,139. The prevalence of RA in 2020 was 99.2 per 100,000 (95% CI 98.2-99.8), with the highest prevalence in the southern region at 135.9 per 100,000 (95% CI 132.2-139.6). Most cases were among women (78.3%), and the highest prevalence was observed in patients aged 60-69 years, at 294.5 per 100,000 (95% CI 290.3-298.6). The incidence of RA increased from 2018 to 2019 but slightly decreased in 2020, reported at 18.6, 18.8, and 18.2 per 100,000 person-years, respectively. Among women, the incidence was 28.6, 28.8, and 27.9 per 100,000 person-years, while in men it was lower, at 8.2, 8.3, and 8.0 per 100,000 person-years from 2018 to 2020. The peak incidence occurred in patients aged 60-69 years, with rates of 58.86, 58.3, and 56.23 per 100,000 person-years from 2018 to 2020. The southern region also had the highest incidence, at 30.4 per 100,000 person-years in 2018, 29.5 in 2019, and 28.1 in 2020. In Thailand, RA was predominantly observed in women of late middle age, with the highest prevalence and incidence occurring in the 60-69 age group. RA was 3.4 times more common in women than in men. The southern region reported the highest prevalence and incidence of RA.