title: Cigarette smoking and the risk of head and neck cancer in the Japanese population: a systematic review and meta-analysis.
abstract: OBJECTIVE
  Although cigarette smoking is a well-established risk factor for head and neck cancer, the impact of smoking on head and neck cancer might vary among geographic areas. To date, however, no systematic review of cigarette smoking and head and neck cancer in the Japanese population has yet appeared.
  
  
  METHODS
  We conducted a systematic review of previous epidemiological studies for cigarette smoking and head and neck cancer among Japanese. Evaluation of associations was based on the strength of evidence ('convincing', 'probable', 'possible' or 'insufficient') and the magnitude of association ('strong', 'moderate', 'weak' or 'no association'), together with biological plausibility as previously evaluated by the International Agency for Research on Cancer. A meta-analysis was conducted to obtain summary estimates for the overall magnitude of association.
  
  
  RESULTS
  We identified five cohort studies and 12 case-control studies. Four of five cohort studies and 11 of 12 case-control studies showed a strong positive association between cigarette smoking and head and neck cancer. Nine of 12 studies indicated a dose-response relationship between cigarette smoking and the risk of head and neck cancer. Meta-analysis of 12 studies indicated that the summary relative risk for ever smokers relative to never smokers was 2.43 (95% confidence interval: 2.09-2.83). Summary relative risks for current and former smokers relative to never smokers were 2.68 (2.08-3.44) and 1.49 (1.05-2.11), respectively.
  
  
  CONCLUSIONS
  Cigarette smoking is a convincing risk factor for head and neck cancer in the Japanese population.
authors.affiliation: Department of Preventive Medicine, Kyushu University Faculty of Medical Sciences, Fukuoka Department of Epidemiology, Nagoya University Graduate School of Medicine, Nagoya.
authors.forename: Yuriko N
authors.initials: YN
authors.lastname: Koyanagi
authors.affiliation: Division of Molecular Medicine, Aichi Cancer Center Research Institute, Nagoya Department of Epidemiology, Nagoya University Graduate School of Medicine, Nagoya kmatsuo@aichi-cc.jp.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya Department of Epidemiology, Nagoya University Graduate School of Medicine, Nagoya.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Ito
authors.affiliation: Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Nagoya.
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.affiliation: Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Gifu.
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.affiliation: Center for Cancer Control and Statistics, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka.
authors.forename: Tomio
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: Department of Epidemiology, Radiation Effects Research Foundation, Hiroshima.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sadakane
authors.affiliation: Department of Preventive Medicine, Faculty of Medicine, Saga University, Saga.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Department of Public Health, Hokkaido University Graduate School of Medicine, Sapporo.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.affiliation: Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Sugawara
authors.affiliation: Department of Epidemiology and International Health, International Clinical Research Center, National Center for Global Health and Medicine, Tokyo.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo.
authors.forename: Norie
authors.initials: N
authors.lastname: Sawada
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.forename: Motoki
authors.initials: M
authors.lastname: Iwasaki
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Otani
authors.forename: Norie
authors.initials: N
authors.lastname: Sawada
authors.forename: Taichi
authors.initials: T
authors.lastname: Shimazu
authors.forename: Taiki
authors.initials: T
authors.lastname: Yamaji
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Tsubono
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nishino
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.forename: Hidemi
authors.initials: H
authors.lastname: Ito
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.forename: Tomio
authors.initials: T
authors.lastname: Nakayama
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sadakane
mesh_terms: D044466:Asian People; D016208:Databases, Factual; D004305:Dose-Response Relationship, Drug; D006258:Head and Neck Neoplasms / Q000453:epidemiology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking
keywords: Japanese; cigarette smoking; epidemiology; head and neck cancer; systematic review