Collaboration in Civic Spheres

Study: Pre-Pregnancy Drinking Boosts Breast Cancer Risks

by Matt Rosenberg September 4th, 2013

A new study funded by the National Cancer Institute finds that between the onset of menstruation and first pregnancy the risk of breast cancer for women grows 11 percent for each 10 grams of alcohol consumed per day and 34 percent if average consumption equals 15 grams per day, or about 1.3 drinks. Even for non-drinking women, the longer the gap between start of menstruation and first pregnancy, the greater the breast cancer risk: the study said women who reported no alcohol consumption at all but waited more than 10 years between menstruation onset and first pregnancy, had a 26 percent increased risk of breast cancer. There are a range of other risk factors. These appear to include certain types of oral contraceptives, according to a report from Seattle-area researchers last year.

The new study was published online in late August in the Journal of the National Cancer Institute, in full and available free of charge. It is based on data from 91,005 women respondents to the Nurses Health Study 2. They had no previous cancer history and were tracked over a 10-year period after answering questions about early alcohol consumption.

The team of 10 researchers producing the study was led by Dr. Graham Colditz of the Washington University School of Medicine in St. Louis, and the study was approved by the Human Subjects Committees at Harvard University’s public health school and that of Brigham and Women’s Hospital.

First pregnancy is an important marker in cancer risk phasing, writes Colditz, because it “induces long-term hormonal changes, including reduced prolactin and estrogen and increased sex hormone-binding globulin, which may provide further protection against breast cancer.” The study notes that alcohol consumption by adult women has already been identified as a risk factor in breast cancer by the International Agency for Research on Cancer, but that in other prior research “the risk attributable to alcohol intake during adolescence and early adulthood” had been “inconclusive.”

The study also looked at the increased risk of proliferative benign breast disease or BBD from early drinking and determined a 16 percent increase in the risk for that condition for each 10 grams per day average alcohol consumption between menstruation onset and first pregnancy. BBD can serve as a precursor for later breast cancer.

There are a range of other risk factors related to breast cancer and only about four percent of new U.S. cases in 2013 would be primarily attributable to drinking before first pregnancy, the authors note. Still, that would be more than 11,600 cases this year, they add. According to the American Cancer Society, other breast cancer risk factors include inherited DNA mutations which weaken tumor suppressor genes, family history of breast cancer, being 55 or older, having dense breast tissue, early onset of menstruation (before age 12) and later onset of menopause (after age 55).

Another risk factor may relate to type of oral contraceptives used by women. In a separate study preliminary published last year researchers at the Group Health Cooperative HMO in Seattle, and the University of Washington found a particularly strong association between invasive breast cancer and having taken in the last year an oral contraceptive with either high-dose estrogen or the progestin ethynodial diacetate.

In a data visualization and article published earlier this year, we reported on National Cancer Institute breast cancer incidence data by state which showed that for the most recent year then available, 2009, Washington had the highest per capita rate.


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