Smoking Research Today is a free monthly online journal that collates and summarizes the latest research about Smoking, including details on cigarettes, cancer, lung, tar, nicotine. | ||||||||
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Smoking cigarettes before first childbirth and risk of breast cancer.Ha M, Mabuchi K, Sigurdson AJ, Freedman DM, Linet MS, Doody MM, Hauptmann M Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA. minaha@dankook.ac.kr Inconsistent epidemiologic findings on cigarette smoking and female breast cancer risk may reflect insufficient assessment of smoking onset and amount relative to reproductive events. To determine the risk of breast cancer associated with smoking during different periods of reproductive life, the authors evaluated 906 incident breast cancer cases in a nationwide cohort of 56,042 female US radiologic technologists (1983-1998) who responded to two questionnaire surveys. After they accounted for age, birth cohort, and established breast cancer risk factors, smoking-related breast cancer risks differed by smoking during three reproductive time periods (p = 0.003), with a statistically significant 3% increase per pack-year of smoking between menarche and first childbirth (relative risk = 1.03, 95% confidence interval: 1.02, 1.05) and no significant association for smoking after first childbirth. Risk also increased with younger age at smoking initiation (p-trend = 0.06), after adjustment for pack-years of smoking before and after first childbirth, indicating an independent effect of age at smoking initiation. The findings from this study suggest that sensitivity of the female breast to tobacco carcinogens is increased during adolescence and early adulthood but decreases after first childbirth, when most breast tissue has terminally differentiated. Published 14 June 2007 in Am J Epidemiol, 166(1): 55-61.
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