Boston, MA (PressExposure) February 18, 2011 -- Researchers at Brigham and Women's Hospital found that heavy and prolonged smoking initiated before menopause may be associated with a modest increase in the risk of developing breast cancer. These findings are published in the January 24 issue of Archives of Internal Medicine.
"Breast cancer is the most common cancer to affect women worldwide," said lead study author Fei Xue, MD, ScD, of the Department of Obstetrics and Gynecology at BWH. "Knowing that tobacco smoke contains potential human breast carcinogens, we wanted to determine whether there was a connection between smoking and breast cancer risk."
Using data collected from the Nurses' Health Study, the researchers examined the records of 111,140 women from 1976 to 2006 for active smoking and 36,017 women from 1982 to 2006 for passive, or secondhand, smoking. They found that the development of breast cancer was associated with a higher quantity of current and past smoking, smoking for a longer period of time, younger age at smoking initiation and more pack-years (the number of packs per day and the number of years that quantity was smoked) of smoking. Women who smoked more than 30 pack-years between menarche and menopause had a 28% higher incidence of breast cancer than never smokers.
Smoking before menopause was positively associated with breast cancer risk, though smoking after menopause was shown to potentially be associated with a slightly decreased breast cancer risk. "This difference may suggest an antiestrogenic effect of smoking among postmenopausal women that may further reduce their already low endogenous estrogen levels," said senior study author Karin B. Michels, ScD, PhD, of the Department of Obstetrics and Gynecology at BWH, noting the many other serious health risks of smoking at any age, including after menopause. Researchers found that passive smoking in childhood or adulthood was not associated with an increase in breast cancer risk.
"Though we did not find an association between light to moderate or passive smoking and breast cancer risk, it is important to highlight the many potential health risks beyond breast cancer that have a proven association with smoking," said Dr. Xue.
Brigham and Women's Hospital (BWH) is a 777-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare, an integrated health care delivery network. In July of 2008, the hospital opened the Carl J. and Ruth Shapiro Cardiovascular Center, the most advanced center of its kind. BWH is committed to excellence in patient care with expertise in virtually every specialty of medicine and surgery. The BWH medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in quality improvement and patient safety initiatives and its dedication to educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Biomedical Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, involving more than 860 physician-investigators and renowned biomedical scientists and faculty supported by more than $416 M in funding. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative. For more information about BWH, please visit Brigham and Women's Hospital.