RESEARCH ARTICLE Passive Smoking and Breast Cancer Risk among Non-Smoking Women: A Case- Control Study in China

Background The role of passive smoking on breast cancer risk was unclear. This study aimed to evalu-ate the association between passive smoking and breast cancer risk among Chinese women. Methods/Principal Findings A hospital-based case-control study, including 877 breast cancer cases and 890 controls, frequency-matched by age and residence, was conducted. A structured questionnaire was used to collect information on passive smoking history through face-to-face interview by trained interviewers. Unconditional logistic regression models were used to estimate the as-sociation between passive smoking and breast cancer risk. A positive association between any passive smoking exposure and breast cancer risk was observed. Compared with women who were never exposed to passive smoking, women who were ever exposed had a higher breast cancer risk, with the adjusted odds ratio (OR) and 95 % confidence interval (CI) of 1.35 (1.11-1.65). Similar result was found on home passive smoking exposure an