title: Duration of cigarette smoking is a risk factor for oropharyngeal cancer mortality among Japanese men and women: the Ibaraki Prefectural Health Study (IPHS).
abstract: OBJECTIVE
  The relationship between duration of cigarette smoking and the risk of oropharyngeal cancer has not been studied in the general Japanese population. Thus, the aim of the present study was to examine the relationship between the duration of cigarette smoking and the risk of oropharyngeal cancer mortality in the Japanese population.
  
  
  METHODS
  In this large cohort study, 32,989 men and 63,894 women, ages 40-79 years, who completed health check-ups in Ibaraki Prefecture, Japan, in 1993 were followed through 2008. Oropharyngeal cancer mortality was identified by death certificates. Smoking habits were divided into five categories, and years of cigarette smoking and pack-year classifications were divided into four categories. Hazard ratios and 95% confidence intervals for oropharyngeal cancer mortality were calculated by use of the Cox proportional hazards regression models.
  
  
  RESULTS
  During the follow-up period, deaths from oropharyngeal cancer occurred in 38 of 32,989 men and 31 of 63,894 women. The multivariate hazard ratios for oropharyngeal cancer mortality were significantly greater for those subjects currently smoking for 40 years or longer (hazard ratio: 4.22, 95% confidence interval: 1.23-14.51), and they were greater with longer years of cigarette smoking among men (P for trend = .027).
  
  
  CONCLUSIONS
  Smoking duration can be a risk factor for oropharyngeal cancer mortality in the Japanese population.
authors.affiliation: Department of Public Health, Dokkyo Medical University School of Medicine, Tochigi, Japan. n-saitou@dokkyomed.ac.jp
authors.forename: Nobue
authors.initials: N
authors.lastname: Saito
authors.forename: Toshimi
authors.initials: T
authors.lastname: Sairenchi
authors.forename: Fujiko
authors.initials: F
authors.lastname: Irie
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Iso
authors.forename: Kyoko
authors.initials: K
authors.lastname: Iimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Muto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ota
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D044466:Asian People / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007407:Interviews as Topic; D007564:Japan / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009959:Oropharyngeal Neoplasms / Q000209:etiology / Q000401:mortality*; D011159:Population Surveillance; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D012959:Socioeconomic Factors; D013997:Time Factors
keywords: Cohort studies; Oropharyngeal neoplasms; Risk factors; Smoking