Nationwide population-based epidemiologic study of rheumatoid arthritis in Taiwan

Objectives Epidemiological studies of rheumatoid arthritis in Asia are rare. The aim of this research was to study the epidemiology and associated medical expenses of rheumatoid arthritis in Taiwan. Methods Cases of rheumatoid arthritis, based on the 1987 American College of Rheumatology criteria, were retrieved from the National Health Insurance Research Database with corresponding International Classification of Diseases, Ninth Revision code (ICD-9) 714.0 from January 2000 to December 2007, and limited to those 16 years and older. Age- and sex-specific incidences were estimated by dividing the incidence number by population data obtained from the Department of Statistics, Ministry of the Interior. Results There were a total of 40,995 cases. The average age-adjusted annual incidence rate was 15.8 per 100,000. The adjusted incidence rates were very stable at 20.9-25.2/100,000/year and 7.0-8.2/100,000/year for females and males, respectively, during the study period. The adjusted average incidence ratio of females/males was 3.1. The age-specific incidence peaked in the 60-64 and 70-74 year age groups for females and males, respectively. The adjusted prevalence rate increased steadily during the study period from 57.7/100,000 in 2000 to 99.6/100,000 in 2007. The average total yearly expense per patient increased from 1,155 United States Dollars (USD) in 2000 to 1,821 USD in 2007. Sicca syndrome (ICD-9 code 710.2) was the most common co-existing ICD-9 code. Conclusion This is the first incidence study based on the 1987 American College of Rheumatology criteria in Asia. The prevalence rate based on these criteria was lower than in previous Asia studies. The medical expenses increased continuously.