To date, research on the effects of smoking on breast cancer risk has yielded conflicting and inconclusive results. Some scientists propose that the timing of cigarette smoke exposure is the key to whether smoking increases a woman’s risk of breast cancer. For instance, in puberty just after the first menstrual period, breast tissue is changing and hormones are very active. Exposure to cancer-causing agents in tobacco at this time might cause damage that will later lead to breast cancer. Research published in the October 5, 2002 issue of
suggests that women who started smoking within five years after starting menstruation are more likely to develop breast cancer before menopause than women who didn’t smoke in this timeframe.
About the Study
Canadian researchers enrolled 1018 women with breast cancer and 1025 women without breast cancer into this case-control study. Cases were breast cancer patients younger than 75 listed in the British Columbia cancer registry as diagnosed with breast cancer between June 1, 1988 and June 30, 1989. Controls were women of the same age without breast cancer who were randomly selected from the British Columbia provincial voters list.
Participants completed a mailed questionnaire about personal and family medical history, ethnic origin, menstrual and reproductive history, lifetime smoking, alcohol consumption, age, weight, height, breast-feeding, and use of birth control pills or hormone replacement therapy. Cases and controls were also classified according to their current menopausal status: premenopausal (average age 43) or postmenopausal (average age 64).
Researchers compared the smoking histories of premenopausal cases with premenopausal controls. In separate analyses, they compared the smoking histories of postmenopausal cases with postmenopausal controls.
Among premenopausal women, those who started smoking within five years after their first period were 70% more likely to develop breast cancer than women who did not smoke in the same timeframe. However, smoking did not increase the risk of breast cancer among postmenopausal women. These results have been adjusted to account for the effects of other risk factors for breast cancer, such as age, personal or family history of breast cancer, age at first period, ethnicity, education, alcohol intake, and use of hormonal drugs.
According to these findings, although smoking in the five years after first menstruation may increase risk of breast cancer before menopause, it does not affect the risk of breast cancer that develops after menopause. It may be that postmenopausal breast cancers are influenced more by environmental factors throughout life than by exposure to cigarette smoke early in adolescence.
Although these findings suggest that smoking during puberty increases your risk of developing breast cancer before menopause, this study has its limitations. These findings rely on women to accurately report how old they were when they started menstrual periods and when they started smoking. This information may be difficult to recall accurately several decades after the fact. In addition, the researchers did not collect information on dietary habits and exposure to secondhand smoke—two factors that may affect breast cancer risk.
How Does This Affect You?
These results provide yet another reason not to start smoking during the teen years. We know that smoking in the teen years increases the likelihood of developing a lifelong addiction to cigarettes that puts you at high risk for heart disease and lung cancer, among many other conditions, later in life. This research suggests that for women, smoking in the teen years also increases the risk of developing breast cancer before menopause, which is usually around age 50.
In addition, these findings shed light on why previous research on smoking and breast cancer has been conflicting and inconclusive. It appears that the effects of smoking on breast cancer risk may be specific to certain times in a woman’s life.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a