Is the incidence of rheumatoid arthritis rising?: Results from Olmsted County, Minnesota, 1955–2007

To examine trends in the incidence and prevalence of rheumatoid arthritis (RA) from 1995 to 2007.

To augment our preexisting inception cohort of patients with RA (1955-1994), we assembled a population-based incidence cohort of individuals >or=18 years of age who first fulfilled the American College of Rheumatology 1987 criteria for the classification of RA between January 1, 1995 and December 31, 2007 and a cohort of patients with prevalent RA on January 1, 2005. Incidence and prevalence rates were estimated and were age-and sex-adjusted to the white population in the US in 2000. Trends in incidence rates were examined using Poisson regression methods.