Incidence and prevalence of rheumatoid arthritis in the county of Troms, northern Norway

Objective. To investigate the population incidence and prevalence of rheuma toid arthritis (RA) in persons above the age of 20 in the county of Troms, northern Norway, during the period 1987-1996. Methods. All records of patients with RA registered at the Department of Rh eumatology at the University Hospital of Tromso during the years 1987 to 19 96 were reviewed. The diagnosis of RA was set in accordance with the 1987 A merican Rheumatism Association criteria, and the population data were based on the 1989 and 1993 census. Total and age-specific incidence rates were c alculated as number of new cases per 100,000 inhabitants and year. Age adju sted incidence rates were obtained by the direct method. Prevalence rates o f RA for January 1, 1989, and January 1, 1994, were estimated. Results. The total annual incidence rate for the period 1987-1996 was 28.7/ 100,000 per year (36.0/100,000 in women and 21.4/100,000 in men). No signif icant difference in incidence rates was found between the periods 1987-1991 and 1992-1996. Total prevalence of RA was 0.39% in 1989 and 0.47% in 1994. The corresponding data for women and men were 0.54% and 0.24% in 1989, and 0.63% and 0.30% in 1993, respectively. Conclusion, We found a rather low incidence and prevalence of RA in the cou nty of Troms in northern Norway. Females contracted RA significantly more o ften than males. There was no change in incidence rates during the observat ion period, lending no support to suggestions of a continuously decreasing occurrence of RA.