Active and Passive Smoking Increases Postmenopausal Breast Cancer Risk
Women who are exposed to tobacco smoke, either by active or passive smoking, are at a greater risk of developing cancer after menopause than women who have never smoked , finds a new study published in the journal BMJ.
Active Smoking and Extensive Exposure to Second-Hand Smoke Increase Risk
A research team, led by Dr. Juhua Luo from West Virginia University and Dr. Karen Margolis from the HealthPartners Research Foundation, used data from the 1993-98 Women’s Health Initiative Observational study to determine links between active smoking, exposure to second-hand smoke, and breast cancer. Information from almost 80,000 women between the ages of 50 to 79 was used for the analysis.
The participants were asked questions about smoking status (current or former), the age at which they started smoking, and the number of cigarettes smoked in a day. Former smokers were asked the age they quit smoking. Information was also gathered on second-hand smoke exposure in both childhood and as adults.
In total, 3,250 cases of invasive breast cancer were identified during the ten years of follow-up.
The researchers found that smokers have a 16% increased risk of developing breast cancer after menopause. The highest risk was found among women who smoked the longest and who began smoking at an earlier age or before their first full-term pregnancy.
Quitting smoking helped to reduce the risk, but former smokers still had a 9% increase in risk over lifetime nonsmokers. The increased risk of breast cancer continued for up to 20 years after an individual stopped smoking.
For non-smoking women who had extensive exposure to passive smoking - for example, over 10 years’ exposure in childhood, 10 years’ exposure in the workplace or 20 years of exposure as an adult at home – the risk of developing breast cancer was 32% greater.
The authors stress, however, that their analysis of the link between breast cancer and secondhand smoke was restricted to the most extensive passive smoking category and therefore more research is needed to confirm these findings.
"Our findings highlight the need for interventions to prevent initiation of smoking, especially at an early age, and to encourage smoking cessation at all ages", Dr Margolis concludes. “There are a lot of risk factors beyond our control, but this is a lifestyle change women can make that will have an impact.”
Juhua Luo, Karen L Margolis, Jean Wactawski-Wende, Kimberly Horn, Catherine Messina, Marcia L Stefanick, Hilary a Tindle, Elisa Tong, Thomas E Rohan. Association of active and passive smoking with risk of breast cancer among postmenopausal women: a prospective cohort study. BMJ, 2011; DOI: 10.1136/bmj.d1016
Paolo Boffetta, Philippe Autier. Is breast cancer associated with tobacco smoking? BMJ, 2011; DOI:10.1136/bmj.d1093
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