RT Journal Article
SR Electronic
T1 Breast Cancer Risk Among Women Who Start Smoking as Teenagers
JF Cancer Epidemiology Biomarkers & Prevention
JO Cancer Epidemiol Biomarkers Prev
FD American Association for Cancer Research
SP 61
OP 66
VO 14
IS 1
A1 Gram, Inger T.
A1 Braaten, Tonje
A1 Terry, Paul D.
A1 Sasco, Annie J.
A1 Adami, Hans-Olov
A1 Lund, Eiliv
A1 Weiderpass, Elisabete
YR 2005
UL http://cebp.aacrjournals.org/content/14/1/61.abstract
AB Objective: To examine the effect of smoking on breast cancer risk in a large population-based cohort of women, many of whom started smoking as teenagers. Methods: We followed 102,098 women, ages 30 to 50 years, completing a mailed questionnaire at recruitment to the Norwegian-Swedish Cohort Study in 1991/1992, through December 2000. We used Cox proportional hazard regression models to estimate relative risk (RR) of breast cancer associated with different measures of smoking initiation, duration, and intensity adjusting for confounding variables. We conducted analyses on the entire study population, among women who had smoked for at least 20 years, among nondrinkers, and separately for each country. Results: Altogether, 1,240 women were diagnosed with incident, invasive breast cancer. Compared with never smokers, women who smoked for at least 20 years and who smoked 10 cigarettes or more daily had a RR of 1.34 (95% CI, 1.06-1.70). Likewise, those who initiated smoking prior to their first birth (1.27, 1.00-1.62), before menarche (1.39, 1.03-1.87), or before age 15 (1.48, 1.03-2.13) had an increased risk. In contrast, women who had smoked for at least 20 years, but started after their first birth, did not experience an increased breast cancer risk. The increased RR associated with smoking was observed among nondrinkers of alcohol, women with and without a family history of breast cancer, premenopausal and postmenopausal women, and in both countries. Conclusion: Our results support the notion that women who start smoking as teenagers and continue to smoke for at least 20 years may increase their breast cancer risk.