Smoking slightly increases breast cancer risk

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For women looking for another reason to quit smoking, a new study strongly supports the notion that smoking increases the risk of breast cancer. In a study published in the Archives of Internal Medicine, the researchers followed over 111,000 active smokers from the Nurses’ Health Study from 1976 to 2006 and approximately 36,000 passive smokers from the same cohort between 1982 and 2006. They reported that for every 20 pack-years of smoking after a woman's first period, her risk of developing cancer was slightly elevated — by between 7 and 15 percent — compared to those who had never smoked. Meanwhile, they found post-menopausal smoking and breast cancer seemed to have an opposite relationship — a somewhat reduced risk of breast cancer. Passive exposure to smoking in both childhood and adulthood was not associated with increased breast cancer risk.

Given the large number of patients in this study, the findings demonstrate a strong dose-response relationship, says ACSH's Dr. Gilbert Ross. “The more a woman smokes and the earlier she starts, the higher her breast cancer risk, although the effect is small. In light of this study, I believe it’s time to add breast cancer to the list of smoking-related cancers.”

ACSH's Dr. Elizabeth Whelan believes that these data may not seem like anything new, “but over the past few decades some researchers believed smoking might decrease breast cancer by reducing estrogen production. This study gives the lie to that theory. So this is yet another cancer related to inhaling the products of combustion — cigarette smoke.”