International Variations and Trends in the Incidence of Breast Cancer in Older Women.

This article explores age-related variations in breast cancer mortality in the western world and analyzes potential risk factors for older women. The highest breast cancer mortality rates are observed in England, Wales, and Denmark; the United States, Canada, Sweden, central and southern Europe have intermediate mortality rates; and Latin America and Russia have the lowest rates. Three case-control studies involving over 4000 Italian women demonstrate that age at menarche is a risk factor only for premenopausal women; multiparity (>5 births) increases the risk of breast cancer for women under age 35 years but reduces the risk of breast cancer for older women. Obesity is a risk factor only for postmenopausal women, and the influence of other risk factors, such as age at first birth, family history and late menopause, does not show age-related variations. The influence of diet and steroidal contraceptives on the breast cancer rate in older women is not established.