Wendy Chen, MD, MPH
These findings are published in the November 2 issue of the Journal of the American Medical Association.
In previous studies, a high consumption of alcohol has been found to be associated with an increased risk of breast cancer. However, the effect of moderate and low levels of drinking have not been well quantified been investigated. “In addition to looking at the effects of all drinking, we wanted to investigate how consumption at different times of adult life and the role of drinking patterns, like frequency of drinking and ‘binge’ drinking, effected the risk as well” said lead study author Wendy Y. Chen, MD, MPH, a researcher at BWH.
The researchers examined the association of breast cancer with alcohol consumption during adult life, including quantity, frequency, and age at consumption. The study included 105,986 women enrolled in the Nurses’ Health Study who were followed up from 1980 until 2008 with an early adult alcohol assessment and 8 updated alcohol assessments. The primary outcome the researchers measured was the risk of developing invasive breast cancer.
During the follow-up period, there were 7,690 cases of invasive breast cancer diagnosed among the study participants. Analyses of data indicated that a low level of alcohol consumption (5.0 to 9.9 grams per day, equivalent to 3-6 glasses of wine per week) was modestly but statistically significantly associated with a 15 percent increased risk of breast cancer. In addition, women who consumed at least 30 grams of alcohol daily on average (at least 2 drinks per day) had a 51 percent increased risk of breast cancer compared with women who never consumed alcohol.
The researchers also found that when examined separately, alcohol consumption levels at ages 18 to 40 years and after age 40 years were both strongly associated with breast cancer risk. The association with drinking in early adult life still persisted even after controlling for alcohol intake after age 40 years. “What this means, is that at any age, after drinking at any intensity, a woman can still potentially decrease her risk of breast cancer by decreasing alcohol consumption. It’s never too late,” said Dr. Chen.
Binge drinking, but not frequency of drinking, was also associated with breast cancer risk after controlling for cumulative alcohol intake.
The authors add that although the exact mechanism for the association between alcohol consumption and breast cancer is not known, one probable explanation may involve alcohol’s effects on circulating estrogen levels.
“Our results highlight the importance of considering lifetime exposure when evaluating the effect of alcohol, and probably other dietary factors, on the carcinogenesis process,” concludes Dr. Chen. “However, an individual will need to weigh the modest risks of light to moderate alcohol use on breast cancer development against the beneficial effects on cardiovascular disease to make the best personal choice regarding alcohol consumption.”