We estimated the incidence of rheumatoid arthritis in the southern part of Denmark from 1995 to 2001. At a rheumatology hospital serving a population of about 200 000 people over the age of 15, medical records were scrutinized. As case definition we used the tree and list format of 1987 American College of Rheumatology criteria for rheumatoid arthritis. The mean annual incidence rate per 100 000 person years was 40 in females, 21 in males, and 31 in females and males combined. The incidence of rheumatoid arthritis in Denmark is in accordance with recent studies from North America, the UK, and Northern European countries. The aetiology of rheumatoid arthritis is unknown but this study indicates that in these populations the exposure to non-genetic host and environmental aetiological factors is similar.
Keywords: Rheumatoid arthritis; epidemiology; incidence; register.