The incidence of thoracic vertebral fractures in a Japanese population, Hiroshima and Nagasaki, 1958-86.

The incidence of thoracic vertebral fractures (TVF) in a Japanese population of 14,607 individuals from Hiroshima and Nagasaki was determined by sex, age, birth cohort, and exposure to atomic bomb radiation. The diagnosis of TVF was based on lateral chest radiographs made from 1 July 1958 to 28 February 1986. The subjects, who were born between 1880 through 1939, were categorized by sex into 10-year birth cohorts. TVF incidence increased by a factor of 1.7 in all birth cohorts with each 10-year increase in age in females, but did not increase with age in males. The incidence was significantly lower in the younger birth cohorts in both sexes. The incidence declined by a factor of 0.5 in males and 0.6 in females for each 10-year decrease in the year of birth. TVF incidence did not differ between the cities, and no correlation with atomic bomb radiation exposure was demonstrated.