Passive or active smoking, which is more relevant to breast cancer.

OBJECTIVE To examine the risk of breast cancer associated with passive and active smoking and to explore risk heterogeneity among studies. METHODS We conducted this study in Iran during the year 2006. Fifteen published studies on smoking and breast cancer met the defined criteria. Pooled odds ratio (OR) estimates for female breast cancer were calculated. The active and passive smokers were compared with women categorized as never regularly exposed to tobacco smoke. RESULTS The pooled risk estimate for breast cancer associated with passive smoking among non-smokers was 1.38 (95% confidence interval [CI]; 1.16-1.65). The pooled OR for active smokers was 1.25 (95% CI; 1.11-1.41). Also, the combined OR for passive and active smokers related to breast cancer was 1.30 (95% CI; 1.17-1.45). CONCLUSION Based on the results of the pooled analysis, it can be concluded both passive and active smoking equally increase the risk of female breast cancer.