Rheumatoid arthritis and gout in Hiroshima and Nagasaki, Japan: A prevalence and incidence study

Abstract

Observations of definite rheumatoid arthritis in a fixed population of 11,393 atomic bomb survivors in Hiroshima and Nagasaki for the period April, 1965 through December, 1966, based on a prospective study designed for specific detection of rheumatoid arthritis are reported. Routine complete physical examinations were performed on all persons in the sample. Screening procedures utilized in all subjects included: completion of a questionnaire and performance of ‘rheumatoid factor’ tests. When indicated by results of clinical and laboratory examinations, PA roentogenograms of the hands and wrists were obtained. A rheumatologist (ID) reviewed the medical records of all individuals in whom there was evidence to suspect rheumatoid arthritis. 1303 of individual patients whose earlier examinations indicated the need, were recalled for clarification, confirmation and classification of their disease. The time of onset of disease was also established. The prevalence rate of definite rheumatoid arthritis was 0.38 per cent for males and 0.65 per cent for females, over 20 years of age, and 0.55 per cent for both sexes. This prevalence rate for females was significantly lower than the age adjusted rate in a comparable population in Tecumseh, but this was not so for males. The incidence rate of definite rheumatoid arthritis was 0.07 per cent for males and 0.11 per cent for females per year. In this sample of Japanese, the prevalence rate of positive latex tube fixation tests for the rheumatoid factor was consistently higher than reported for the comparable Tecumseh, Michigan, population. Adequate explanation of this difference is not now available. The relationship between rheumatoid arthritis or rheumatoid factor and environmental factors such as education, occupation, and other physical findings such as level of serum uric acid and blood pressure was studied. No relationship was detected between prevalence and incidence of rheumatoid arthritis and exposure to radiation from the atomic bombs. The age-sex specific mean uric acid values for Japanese men and women were very similar to those in a Caucasian population. In this population survey, as reported in others, very few cases of gout were detected.