title: Lack of an association between passive smoking and incidence of female breast cancer in non-smokers: evidence from 10 prospective cohort studies.
abstract: BACKGROUND
  Several case-control studies have suggested that passive smoking may increase the incidence of female breast cancer. However, the results of cohort studies have been inconsistent in establishing an association. The present study evaluated the association between passive smoking and incidence of female breast cancer through a meta-analysis of prospective cohort studies.
  
  
  METHODS
  Relevant articles published before August 2012 were identified by searching the electronic databases PubMed, Embase, and Web of Science. Pooled relative risks (RRs) were determined with either a fixed or random effects model and were used to assess the strength of the association. Sensitivity and subgroup analyses according to ethnicity, menopausal status, and the period and place of exposure to passive smoking were also performed.
  
  
  RESULTS
  Ten prospective cohort studies involving 782 534 female non-smokers were included in the meta-analysis and 14 831 breast cancer cases were detected. Compared with the women without exposure to passive smoking, the overall combined RR of breast cancer was 1.01 (95% confidence interval: 0.96 to 1.06, P = 0.73) among women with exposure to passive smoking. Similar results were achieved through the subgroup analyses. No evidence of publication bias was observed.
  
  
  CONCLUSIONS
  The results suggest that passive smoking may not be associated with increased incidence of breast cancer. However, the present conclusion should be considered carefully and confirmed with further studies.
authors.affiliation: Department of Cardiovascular Medicine, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Laura
authors.initials: L
authors.lastname: Skrip
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Shengchun
authors.initials: S
authors.lastname: Liu
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods* / Q000706:statistics & numerical data*; D012307:Risk Factors; D014028:Tobacco Smoke Pollution / Q000706:statistics & numerical data*
chemical_list: D014028:Tobacco Smoke Pollution