THE EPIDEMIOLOGY OF RHEUMATOID ARTHRITIS IN ROCHESTER MINNESOTA: A STUDY OF INCIDENCE, PREVALENCE, AND MORTALITY1

Abstract

A study of the incidence and prevalence of rheumatoid arthritis conducted in Rochester, MN, during the period 1950 through 1974 revealed an average annual incidence rate of 28.1 per 100,000 population for males and of 65.7 per 100,000 for females. These rates include classic, definite, and probable cases. Age-specific rates generally increased with age. The secular trend of the incidence in males and females differed. Rates for males, although fluctuating, remained relatively stable throughout the entire 25-year period, whereas rates for females declined dramatically during the last 10 years of the study. The decline was present both in cases presenting as definite at the time of earliest diagnosis and in the probable cases. No explanation was found for the observed decline, but the authors believe that a factor introduced in the 1960s and acting selectively on females has affected the incidence rates. From recent evidence, it could be inferred that oral contraceptives and postmenopausal estrogens are likely causes. Prevalence rates for January 1, 1975, were 4.0 per 1000 for males and 10 per 1000 for females. Among adults, prevalence rates were 5.8 per 1000 for males and 13.4 for females. Mortality among the patients with rheumatoid arthritis was not different from that for the total Olmsted County population.