[Breast cancer and heredity: results of a population case-control study in Girona]

To characterise the relationship between breast cancer and different aspects of the reproductive life, use of drugs and alcohol by family history of breast cancer.

From the cancer registry of Girona, Spain, 330 women were identified with histologically confirmed breast cancer during 1986-1989. For each case, a control woman was selected from a random sample of the population living in the matched area to the case by age (+/- 5 yr.). The information was collected by a personal interview and included: family history of breast cancer, reproductive history, presence of acne during the teenage years, use of oral contraceptives and drugs for sleep and anxiety disorders, and alcohol consumption.

18.5% of breast cancer cases and 8.9% of all controls had a family history of breast cancer. Family history on a first degree relative (mother or sister) was present in 10.6% of the cases and 2.8% of controls, which represented an odds ratio for breast cancer of 3.7 (95% CI, 1.8-7.8) higher than the general population. Women with a first degree family history of breast cancer were at higher risk for breast cancer if they had a history of acne during the teenage period (OR = 2.4; 95% CI, 1.1-5.2) and if they referred long menstrual periods in the early years of menarche (OR = 3.1; 95% CI, 1.3-7.0). Women with no family history had a higher breast cancer risk if they had a late menarche, long menstrual periods, late first full term pregnancy, and history of acne during puberty. Alcohol consumption and use of drugs for anxiety and sleep disorders were associated with a decreased risk of breast cancer.

First degree family history of breast cancer seems to be the best risk indicator for developing breast cancer. Long menstrual periods and presence of acne during puberty may indicate hormonal imbalance that act independently of the family history in breast cancer development.