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Smoking Linked to Higher Risk of Breast Cancer

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Doctors have long suspected some type of link between cigarette smoking and breast cancer risk, but research results have been mixed. A large study has found that smoking increases breast cancer risk in women, especially women who start smoking before they have their first child.

The research was published online on Feb. 28, 2013 by the Journal of the National Cancer Institute. Read the abstract of “Active Smoking and Breast Cancer Risk: Original Cohort Data and Meta-Analysis.”

While many earlier studies found a slight increase in overall breast cancer risk for women who smoke, they didn’t find that smoking more cigarettes per day or smoking for more years increased risk even more. Also, the effects of drinking alcohol affected many of these studies. Alcohol is a risk factor for breast cancer and women who smoke are more likely to drink alcohol. So it was difficult for the researchers to tease out how much only smoking or only drinking alcohol was affecting breast cancer risk.

In this study, researchers looked at information from nearly 74,000 women in the American Cancer Society’s Cancer Prevention Study II Nutrition Cohort, a large long-term study looking at lifestyle factors and cancer prevention. When the study started in 1992, the women were ages 50 to 74. They reported how much they smoked currently, as well as their smoking history. At the beginning of the study:

  • 8% of the women smoked
  • 36% of the women had quit smoking
  • 56% of the women had never smoked

During more than 13 years of follow-up, 3,721 women were diagnosed with breast cancer. The rate of breast cancer was:

  • 24% higher in women who were currently smoking compared to women who never smoked
  • 13% higher in former smokers compared to women who never smoked

The researchers also looked at when the women started smoking:

  • Women who started smoking before their first menstrual period were 61% more likely to be diagnosed with breast cancer than women who never smoked.
  • Women who started smoking after their menstrual periods started but 11 or more years before having their first child were 45% more likely to be diagnosed with breast cancer than women who never smoked.

To try to figure out if smoking by itself – not the combination of smoking and drinking alcohol – raises breast cancer risk, the researchers then divided the women into three new groups based on drinking status: never, former, and currently drink, and looked at their risk of breast cancer. Interestingly, for women who never drank, smoking – now or in the past – wasn’t linked to a higher risk of breast cancer. Women who currently drink or were former drinkers and smoked – now or in the past – did have a higher risk of breast cancer. Ideally, all three groups – women who never drank, women who drank in the past, and women who currently drink – would have a similar risk to prove smoking by itself is a risk factor. Still, the study didn’t show that. The researchers aren’t sure why this happened, but it may be that the numbers of women who never drank were too small to show any effect. So while this study doesn’t absolutely prove that there is a direct link between smoking and higher risk, it does offer more evidence that there’s a strong association between breast cancer risk and smoking.

Smoking can harm your health, including breast health, at any age. If you don’t smoke, don’t start. If you do smoke, find a program or system to help you quit. Quitting is tough, but it’s definitely worth it. The American Lung Association offers a free online smoking cessation program. Local chapters of the American Cancer Society offer the Fresh Start program to help people quit smoking. You also can call the ACS “Quitline” at 1-800-ACS-2345 to get support and free advice on how to stop smoking from trained counselors.

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