The incidence of breast cancer in the United States is around 12% (SOURCE). After evaluating 111,140 participants of the Nurses’ Health Study from 1976 to 2006 for active smoking and 36,017 women from 1982 to 2006 for passive smoking, study makes two valuable points about cigarette smoking and breast cancer.

One, smoking is likely responsible for an increase in risk of about 6%  moving the overall incidence for smokers from 12% to 12.72%. The authors suggest that the results are statistically significant. While that is probably true, I’m not convinced that this is a clinically significant increase. There are many other risk factors that were not included in this focused study, such as weight, overall diet, level of exercise, family history, the presence of other diseases, and so on.

Two, the authors conclude that, “Passive smoking in childhood or adulthood was not associated with BC risk.“ That flies in the face of the standard beliefs about smoking and cancer. There is a regular concern about the effects of what is referred to as second-hand smoke. Recent studies even suggest that as little as one exposure to second-hand smoke can increase a person’s risk for cancer. That statement sure isn’t supported by this study.

Studies abound and it seems that  for every one that takes a position or draws a conclusion, there’s another that refutes it. Instead of enlightening the community, piles of studies with differing conclusions adds to the confusion and threatens to degrade our general health. Conflicting results might be the result of study design or the processes used. They might also be grounded in the fact that outcomes are often influenced by the person(s) performing the study. That means that any and all predisposing facts or beliefs influence what we see.

I have never found the evidence about second-hand smoke to be compelling. Therefore, I applaud the conclusion in this study that reports that second-hand smoke is NOT a factor. While I can agree that constant exposure to cigarette smoke make be a cause of inflammation and, ultimately, cancer, I am not of the opinion that there is always a perfect link between smoking and cancer. If there was, all smokers would get cancer. And that just isn’t the case. My grandmother smoked every day until she died at age 96 – NOT from cancer. My grandfather lived with grandma’s second hand smoke all his life, until he died at age 98. Yes, they were special people, but there are others with similar histories.

Reference: Cigarette Smoking and the Incidence of Breast Cancer
Fei Xue, MD, ScD; Walter C. Willett, MD, DrPH; Bernard A. Rosner, PhD; Susan E. Hankinson, ScD; Karin B. Michels, ScD, PhD
Arch Intern Med. 2011;171(2):125-133