Drinking alcohol before first pregnancy is associated with an increased risk of benign breast disease (BBD) and breast cancer, independent of drinking after first pregnancy, according to a new study published August 28 in the Journal of the National Cancer Institute.
Previous studies have shown that alcohol consumed in the past year affects a woman's breast cancer risk. However, data on the relationship between drinking alcohol during the period of time between a woman's first menstrual period and first pregnancy and the risk of proliferative BBD and breast cancer had not been reported. Breast tissue is particularly susceptible to carcinogens during that period of time.
Ying Liu, M.D., Ph.D., from the Washington University School of Medicine in St. Louis, MO, and colleagues analyzed data from 116,671 female registered nurses, aged 25-44 years, on medical history, reproductive history, and lifestyle. The data were collected using questionnaires as part of the Nurses' Health Study II (NHSII). Alcohol consumption in four age periods were obtained by asking participants about the total number of alcoholic drinks consumed at different ages (ages 15-17, 18-22, 23-30, and 31-40). After excluding women who did not meet the predetermined study criteria, a total of 91,005 women with a history of full-term pregnancy were included in the final analysis. Among these women, 1,609 cases of breast cancer and 970 cases of BBD occurred during the study period. These cases were confirmed by physicians who reviewed information from each patient's medical records.
Drinking alcohol between the first menstrual period and first pregnancy was associated with risk of breast cancer and proliferative BBD, regardless of drinking after the first pregnancy. The data indicated a dose-dependent relationship, which means the more alcohol a woman drinks during that time, the higher her risk of developing breast cancer. Also, the authors observed longer intervals between first menstrual period and first pregnancy showed stronger associations compared with shorter intervals. The authors also report drinking after the first pregnancy was associated with breast cancer risk but not BBD.
The authors write, "The general consistency in the patterns of association between alcohol and risk of proliferative BBD and of breast cancer lends support to the hypothesis that alcohol intake, particularly before first pregnancy when breast tissue is likely at its most vulnerable stage, may play an important role in the etiology of breast cancer." These findings have potentially important implications for breast cancer prevention.