title: Is green tea drinking associated with a later onset of breast cancer?
abstract: BACKGROUND
  Studies have found that tea polyphenols inhibit aromatase. Because of the substantial difference in levels of estrogens between premenopausal and postmenopausal women, the relationship between tea consumption and breast cancer risk may depend on menopausal status.
  
  
  METHODS
  We examined this hypothesis in the Shanghai Women's Health Study, a population-based cohort study of 74,942 Chinese women.
  
  
  RESULTS
  We found a time-dependent interaction between green tea consumption and age of breast cancer onset (p for interaction, 0.03). In comparison with non-tea drinkers, women who started tea-drinking at 25 years of age or younger had a hazard ratio (HR) of 0.69 (95% confidence interval [CI]: 0.41-1.17) to develop premenopausal breast cancer. On the other hand, compared with non-tea drinkers, women who started tea drinking at 25 years of age or younger had an increased risk of postmenopausal breast cancer with an HR of 1.61 (95% CI: 1.18-2.20). Additional analyses suggest regularly drinking green tea may delay the onset of breast cancer.
  
  
  CONCLUSIONS
  Further studies are needed to confirm our findings.
authors.affiliation: Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt-Ingram Cancer Center, Vanderbilt School of Medicine, Nashville, TN 37203-1738, USA. qi.dai@vanderbilt.edu
authors.forename: Qi
authors.initials: Q
authors.lastname: Dai
authors.forename: Xiao-Ou
authors.initials: XO
authors.lastname: Shu
authors.forename: Honglan
authors.initials: H
authors.lastname: Li
authors.forename: Gong
authors.initials: G
authors.lastname: Yang
authors.forename: Martha J
authors.initials: MJ
authors.lastname: Shrubsole
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.forename: Butian
authors.initials: B
authors.lastname: Ji
authors.forename: Wanqing
authors.initials: W
authors.lastname: Wen
authors.forename: Adrian
authors.initials: A
authors.lastname: Franke
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000328:Adult; D017668:Age of Onset; D001141:Aromatase / Q000187:drug effects; D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D002681:China; D005260:Female; D006801:Humans; D008875:Middle Aged; D013662:Tea
chemical_list: D013662:Tea; D001141:Aromatase