Prevalence of rheumatoid arthritis in densely and thinly populated areas in sweden.

The prevalence of rheumatoid arthritis in 1,287 persons living in densely populated areas and 1, 287 persons living in thinly populated areas, matched as to sex, age, occupation and geographical area, was compared. The patient material was obtained in an epidemiological survey of rheumatoid arthritis (ARA definition) performed in Sweden in 1961. 1.6% of the inhabitants in densely populated areas and 2.5% in thinly populated areas had rheumatoid arthritis (classical, definite, probable, possible). The differences were indicative but not significant. Classical plus definite rheumatoid arthritis, however, showed exactly the same prevalences in the two populations (0.5%). Probable plus possible rheumatoid arthritis was indicatively more prevalent in the thinly populated areas (2.0%) than in the densely populated (1.1%).