title: Tea consumption and lung cancer risk: a meta-analysis of case-control and cohort studies.
abstract: OBJECTIVE
  Recent epidemiologic studies, especially cohort and case-control studies, have yielded inconsistent findings regarding the association between tea consumption and risk for lung cancer. The aim of this study was to assess a potential relationship between tea consumption and the incidence of lung cancer worldwide.
  
  
  METHODS
  A systematic literature search of PubMed, Web of Science, the Cochrane Library, Google Scholar, the Chinese Biomedical Database, and Wanfang Database was conducted from 1966 to January 2014 by two investigators. All cohort studies and case-control studies that evaluated the association of tea and lung cancer were included. Summary relative risks (RR) and the corresponding 95% confidence intervals (CIs) were calculated using a random-effects model. Quality assessments were performed using the Newcastle-Ottawa Scale. Heterogeneity was assessed using the Q and I(2) tests, and the source of heterogeneity was detected by meta-regression analysis. Publication bias was evaluated with Egger's regression symmetry test. Subgroup analyses and sensitivity analysis were performed.
  
  
  RESULTS
  Thirty-eight lung cancer studies (26 case-control studies and 12 cohort studies) with 59,041 cases and 396,664 controls were included. Overall tea consumption was significantly associated with decreased risk for lung cancer (RR, 0.78; 95% CI, 0.70-0.87). Subgroup analyses showed that tea consumption was associated with reduced risk for lung cancer in women (RR, 0.76; 95% CI, 0.62-0.93), case-control studies (RR 0.72; 95% CI 0.63-0.83), Western studies (RR, 0.85; 95% CI, 0.75-0.97), and studies in China and Japan (RR, 0.74; 95% CI, 0.62-0.88). Both green tea (RR, 0.75; 95% CI, 0.62-0.91) and black tea (RR, 0.82; 95% CI, 0.71-0.94) were significantly associated with reduced lung cancer risk. No significant association was found in men or in cohort studies.
  
  
  CONCLUSIONS
  Tea consumption may offer some protection against lung cancer.
authors.affiliation: Institute of Nutrition and Healthy Food, Tongji University School of Medicine, Shanghai, China. Electronic address: Lanfangwlf@tongji.edu.cn.
authors.forename: Lanfang
authors.initials: L
authors.lastname: Wang
authors.affiliation: Institute of Nutrition and Healthy Food, Tongji University School of Medicine, Shanghai, China.
authors.forename: Xingwei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Nutrition and Healthy Food, Tongji University School of Medicine, Shanghai, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Pathogen Biology, Tongji University School of Medicine, Shanghai, China.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Department of Preventive Medicine, Tongji University School of Medicine, Shanghai, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li
mesh_terms: D028241:Camellia sinensis; D006801:Humans; D008175:Lung Neoplasms / Q000517:prevention & control*; D028321:Plant Preparations / Q000627:therapeutic use*; D012306:Risk; D013662:Tea
chemical_list: D028321:Plant Preparations; D013662:Tea
keywords: Lung cancer; Meta-analysis; Tea