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The 13th World Conference on Tobacco OR Health

Building capacity for a tobacco-free world

July 12-15, 2006, Washington, DC, USA

Thursday, July 13, 2006 - 3:50 PM

Accumulating Evidence on Passive and Active Smoking and Breast Cancer Risk

Kenneth C. Johnson, PhD, Evidence and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, 120 Colonnade Road, Ottawa, ON K1A OK9, Canada and A. Judson Wells, private citizen, 5 Ingleton Circle, Kennett Square, PA 19348, Kennett Square, PA 19348.

Objective: To examine the risk of breast cancer associated with passive and active smoking and to explore risk heterogeneity between studies.

Methods: Nineteen of 20 located published studies of passive smoking and breast cancer risk among women met basic quality criteria. Pooled risks for breast cancer were calculated for: 1) life-long non-smokers with regular passive exposure to tobacco smoke; and 2) women who smoked. They were compared to women who were never regularly exposed to tobacco smoke.

Results: The pooled risk estimate for breast cancer associated with passive smoking among life-long non-smokers was 1.27 (95% confidence interval (CI), 1.11-1.45). In the subset of 5 studies (all case-control studies) with more complete exposure assessment (quantitative long-term information on the three major sources of passive smoke exposure: childhood, adult residential and occupational), the pooled risk estimate for exposed non-smokers was 1.90 (95%CI, 1.53-2.37). Increased risk was observed in 3 of 4 Asian cohort studies.

The overall premenopausal breast cancer risk associated with passive smoking among lifelong non-smokers was 1.68 (95%CI 1.33-2.12), and 2.19 (95% CI 1.68-2.84) for the 5 of 14 studies with more complete exposure assessment.

For women who had smoked the breast cancer risk estimate was 1.43 (95%CI 1.12-1.80) when compared to women with neither active nor regular passive smoke exposure; 1.98 (95% CI 1.40- 2.81) for more complete and 1.15 (95% CI 0.92-1.43) for less complete passive exposure assessment. Studies with thorough passive smoking exposure assessment implicate passive and active smoking as risk factors for premenopausal breast cancer.

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