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

OBJECTIVE

To investigate the population incidence and prevalence of rheumatoid 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 Rheumatology at the University Hospital of Tromsø during the years 1987 to 1996 were reviewed. The diagnosis of RA was set in accordance with the 1987 American Rheumatism Association criteria, and the population data were based on the 1989 and 1994 census. Total and age-specific incidence rates were calculated as number of new cases per 100,000 inhabitants and year. Age adjusted incidence rates were obtained by the direct method. Prevalence rates of 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 significant 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 1994, respectively.

CONCLUSION

We found a rather low incidence and prevalence of RA in the county of Troms in northern Norway. Females contracted RA significantly more often than males. There was no change in incidence rates during the observation period, lending no support to suggestions of a continuously decreasing occurrence of RA.