Smoking Rises Breast Cancer Risks

Smoking favors cancer, we all have heard this before, but it seems that smoking before menopause (which can occur between 45 and 55 years old), especially before giving birth, could be linked to a slight increase in the risks of developing breast cancer, a new report concludes.

For the study Fei Xue, MD, Sc.D., of Brigham and Woman's Hospital and Harvard Medical School, Boston, and colleagues, collected data from the Nurses' Health Study.

Background information in the article mentions that “breast cancer is the most common cancer to affect women worldwide.

“Tobacco smoke contains potential human breast carcinogens, including polycyclic aromatic hydrocarbons, aromatic amines and N-nitrosamines.”

The researchers analyzed the records of 111,140 women for active smoking, from 1976 to 2006, and 36,017 women for passive (secondhand) smoking, from 1982 to 2006.

The authors said that “in the present study, we created an index of active smoking that integrates quantity, age at which one started smoking and duration of smoking.”

During follow-up, 8,772 breast cancer cases developed.

Breast cancer occurrence was associated with a higher amount of past and current smoking and with smoking for a long period of time.

Also, beginning smoking at a younger age and having many pack years (product of the number of packs per day and the number of years that quantity was smoked) of smoking, rose breast cancer risks.

“Smoking before menopause was positively associated with breast cancer risk, and there were hints from our results that smoking after menopause might be associated with a slightly decreased breast cancer risk,” write the authors.

“This difference suggests an antiestrogenic effect of smoking among postmenopausal women that may further reduce their already low endogenous estrogen levels.”

On the other hand, never smoking and passive smoking in childhood or adulthood were not linked to an increase in breast cancer risk, nor did the exposure to parents smoking in the same house, passive smoking while at work or at home or the number of years living with someone who smoked, even after adjusting for other possible factors.

The authors concluded that “the results suggested that, although an elevated risk for light smokers and moderate smokers was not apparent, heavy smokers who started smoking early in life, smoked for a long duration and smoked a high quantity were at the highest risk of breast cancer, supporting an independent and additive effect from various smoking measures on breast carcinogenesis.”

The report is published in the January 24 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.