© 1980 Oxford University Press
research-article |
Urban–Rural Differential in Breast Cancer Incidence and Mortality in Omisted County, Minnesota, 1935–1974
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* Department of Medical Statistics and Epidemiology, Mayo Clinic and Mayo Foundation Rochester, Minnesota, 55901, USA
Present address: East Baltimore Medical Plan 1031 Aisquith Street, Baltimore, Maryland 21202, USA
Present address: Department of Internal Medicine and Community Medicine, Charles R Drew Postgraduate Medical School Los Angeles, California 90056, USA
Melton III L J [Department of Medical Statistics and Epidemiology, Mayo Clinic, Rochester, Minnesota 55901, USA] Brian D D and Williams R L. Urban-rural differential in breast cancer incidence and mortality in Olmsted County, Minnesota, 1935–1974. International Journal of Epidemiology 1980, 9: 155–158.
Between 1935 and 1974, 580 new cases of breast cancer were diagnosed among the residents of Rochester, and 187 cases were found among the women living in the remainder of Olmsted County, Minnesota. The age-adjusted incidence of breast cancer was 79.1 per 100 000 person-years among Rochester women and 56.3 per 100 000 person-years among the rural women, for an urban-rural ratio of 1.40: 1. The rural incidence increased more rapidly than did the urban incidence during the period of the study, especially among women 50 years old or older; and the urban-rural ratio seemed to decline with time. No convincing explanation for these changes was found, but migration and increasing urbanisation of rural areas may be important factors. The greater urban incidence and the net migration of rural patients with breast cancer into the urban area explain the higher urban mortality rates for breast cancer.
Revised 3 December 1979