The Prevalence of Rheumatoid Arthritis in Different Geographical Areas in Sweden

Abstract

Summary In the general population of 39,418 persons within areas in the counties of Norrbotten (BD), Jämtland (Z), Skaraborg (R), Kristianstad west coast (LV), and Kristianstad east coast (L) in Sweden all the inhabitants over the age of seven (in Norrbotten over the age of 14) were investigated for the total number of cases of rheumatoid arthritis. Re-investigations of non-response (10—20 %) were made. The southernmost and northernmost areas were about 1,500 km apart. Every person was examined naked or seminaked. The diagnostic criteria prepared by the American Rheumatism Association (ARA) were used. In the mathematical calculations it was possible to determine indices for correct comparisons of the prevalences in the different areas. The prevalence for RA (classical, definite probable, possible) in the populations examined was 3.1 per cent. The highest figures were observed in the southern part of the country (L, LV). The prevalences were higher in the coastal areas (in L, LV and BD) than in the inland areas (Z, R). The prevalence was higher in the non-response group than in the primarily investigated group.