A positive family history of breast cancer. Does it effect diminish with age?

To determine whether the influence of family history on the incidence of breast cancer diminishes with age, we studied data from 9000 women: 2712 with breast cancer, 2972 with benign breast disease, and 3316 control subjects. Patients were divided into eight cohorts by age; for each, odds ratios were computed to compare cancer patients with patients who have benign disease and with control subjects for positive family history of breast cancer. For both sets of comparisons, odds ratios are highest for subjects from 30 to 34 years old. After the age of 45 years, odds ratios decline, and after age 60 years the odds of breast cancer occurring in women with a positive family history are no greater than it is in women without such a history. These results suggest that a family history of breast cancer is a determinant of breast cancer only for women under age 60 years. The mechanism through which this is effected needs to be studied.