title: Tobacco smoking and lung cancer risk: an evaluation based on a systematic review of epidemiological evidence among the Japanese population.
abstract: BACKGROUND
  Although tobacco smoking is the best established risk factor for lung cancer, the association is not as strong among Japanese as among Western populations. It would be of value, therefore, to quantify that association in Japan based on a systematic review of epidemiological evidence for the primary prevention of lung cancer.
  
  
  METHODS
  Original data were obtained from MEDLINE searches using PubMed, supplemented with manual searches. The evaluation of associations was based on the strength of evidence and the magnitude of the association, together with biological plausibility as previously evaluated by the International Agency for Research on Cancer. A meta-analysis was also conducted to estimate the summary measure of those associations.
  
  
  RESULTS
  A total of 8 cohort studies and 14 case-control studies were identified, almost all of which consistently showed a strong association of current smoking with the risk of lung cancer. The summary relative risk for current smokers versus never smokers was estimated as 4.39 (95% confidence interval 3.92-4.92) for men and 2.79 (95% confidence interval 2.44-3.20) for women. Cohort studies and case-control studies gave reasonably consistent summary measures. The summary relative risks were 11.7 and 2.30 for squamous cell carcinoma and adenocarcinoma, respectively, in men, and were 11.3 and 1.37 correspondingly in women.
  
  
  CONCLUSIONS
  There is convincing evidence that tobacco smoking strongly increases the risk of lung cancer in the Japanese population, with the relative risk for current smokers compared with never smokers measuring around 4.4 for men and 2.8 for women.
authors.affiliation: Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya, Japan. wakai@aichi-cc.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology*; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D015201:Meta-Analysis as Topic; D012306:Risk; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects*