Fact Sheet #13, March 1988
The relationship between alcohol consumption and the risk of breast cancer is currently the focus of much research. Since alcohol consumption is a modifiable behavior, information regarding its association with breast cancer may offer women a practical way to decrease their risk of developing this disease.
Does the consumption ofalcohol increase the risk of breast cancer?
The results of most studies indicate that there is a weak association between drinking alcoholic beverages and the incidence of breast cancer at low levels of consumption, and that the risk of breast cancer increases as the amount of alcohol consumed increases. In a recent summary of 63 published studies, 65% reported that consuming alcohol wasassociated with an increased risk of breast cancer. These studies involved different populations of women in several countries.
Women who drink alcohol may be different in many ways from those who do not drink alcohol. In order to determine if the consumption of alcohol is associated with breast cancer, researchers must take into account other factors that have been previously shown to influence breastcancer risk. For example, getting older, having a family history of breast cancer, and an earlier age at menarche (the age when a girl has her first menstrual period) are established risk factors for breast cancer. When assessing the influence of alcohol consumption on breast cancer risk, it is important for researchers to account for these as well as other potential risk factors such as diet andsmoking. These factors may be more common among women who drink alcoholic beverages and may actually be contributing to the reported association between alcohol and breast cancer.
Many of the studies of alcohol consumption and breast cancer risk have taken established breast cancer risk factors into account and some have also included other types of habits and behavioral differences, such as dietand smoking. The results of most of these studies suggest that the consumption of alcohol may have an independent and direct effect on a woman's risk of developing breast cancer. However, other researchers are not convinced that alcohol is acting independently and they are continuing to analyze the relationship between alcohol and other lifestyle and personal characteristics.
How much alcohol isthought to increase the risk of breast cancer?
Researchers have reported that there is a weak association between alcohol consumption and breast cancer in women who drink one alcoholic beverage a day. Drinking more, about 2 to 5 drinks per day, may be associated with a rate of breast cancer that is about 40% higher than the rate for non-drinkers. This level of risk is similar in proportion to thatof other well-established risk factors. For example, breast cancer risk is reported to be about 25% higher in women whose age at menarche was 12 years or younger versus 15 years or older. Also, the risk of breast cancer among women whose mother or sister had breast cancer is increased about 50% or more as compared to women who do not have a family history of the disease.
Is there an age at whichthe consumption of alcohol has the greatest effect?
If alcohol is associated with breast cancer risk, it is important to understand whether the age at which a woman starts to drink alcohol is an important factor in this relationship. Some studies have reported that drinking before the age of 30 is more closely tied to breast cancer risk than recent or current drinking habits. Others havereported that current or recent drinking habits have a greater influence on breast cancer rates than drinking at an early age. Lifetime consumption of alcohol has also been suggested as an important factor when determining breast cancer risk. In other words, it may be the total amount of alcohol consumed during a lifetime regardless of the age at which the habit starts that is most important. Although...