Epidemiologic Comparison of Breast Cancer Patients With Early and Late Onset of Malignancy and General Population Controls2

Abstract
A cross-sectional survey of 134 persons with a history of breast cancer and 260 community controls confirmed earlier findings of an increased risk of breast cancer associated with a positive family history for breast disease and the experience of first childbirth at age 25 or older. Also suggested was an increased risk associated with lactation. When cases were divided into early onset (before age 45) and late onset (age 45+) groups, the first two risk factors were significantly associated with early onset cases only, whereas the third was associated with late onset only. Parity, use of hormones, menstrual history, thyroid disease, education, and marital status showed no association with risk of breast cancer. We found that the risk factors may be different for early- and late-onset breast cancer.