Epidemiology of rheumatoid arthritis in developed countries.

The epidemiology of rheumatoid arthritis (RA) has been the subject of 4 international conferences during the past 25 years and the current concepts have recently been renewed in detail elsewhere. This paper will focus on the prevalence and incidence of RA in various geographic areas and ethnic groups, temporal trends in incidence rates, and the role of host, and environmental and genetic factors in disease etiology.