title: Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study.
abstract: OBJECTIVE
  To investigate the association between tea drinking habits in Golestan province, northern Iran, and risk of oesophageal squamous cell carcinoma.
  
  
  METHODS
  Population based case-control study. In addition, patterns of tea drinking and temperature at which tea was drunk were measured among healthy participants in a cohort study.
  
  
  METHODS
  Golestan province, northern Iran, an area with a high incidence of oesophageal squamous cell carcinoma.
  
  
  METHODS
  300 histologically proved cases of oesophageal squamous cell carcinoma and 571 matched neighbourhood controls in the case-control study and 48 582 participants in the cohort study.
  
  
  METHODS
  Odds ratio of oesophageal squamous cell carcinoma associated with drinking hot tea.
  
  
  RESULTS
  Nearly all (98%) of the cohort participants drank black tea regularly, with a mean volume consumed of over one litre a day. 39.0% of participants drank their tea at temperatures less than 60 degrees C, 38.9% at 60-64 degrees C, and 22.0% at 65 degrees C or higher. A moderate agreement was found between reported tea drinking temperature and actual temperature measurements (weighted kappa 0.49). The results of the case-control study showed that compared with drinking lukewarm or warm tea, drinking hot tea (odds ratio 2.07, 95% confidence interval 1.28 to 3.35) or very hot tea (8.16, 3.93 to 16.9) was associated with an increased risk of oesophageal cancer. Likewise, compared with drinking tea four or more minutes after being poured, drinking tea 2-3 minutes after pouring (2.49, 1.62 to 3.83) or less than two minutes after pouring (5.41, 2.63 to 11.1) was associated with a significantly increased risk. A strong agreement was found between responses to the questions on temperature at which tea was drunk and interval from tea being poured to being drunk (weighted kappa 0.68).
  
  
  CONCLUSIONS
  Drinking hot tea, a habit common in Golestan province, was strongly associated with a higher risk of oesophageal cancer.
authors.affiliation: Digestive Disease Research Center, Shariati Hospital, Tehran University of Medical Sciences, 14117 Tehran, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Islami
authors.forename: Akram
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authors.lastname: Pourshams
authors.forename: Dariush
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authors.lastname: Nasrollahzadeh
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authors.lastname: Kamangar
authors.forename: Saman
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authors.forename: Ramin
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authors.lastname: Shakeri
authors.forename: Behnoush
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authors.lastname: Abedi-Ardekani
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authors.lastname: Merat
authors.forename: Homayoon
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authors.lastname: Vahedi
authors.forename: Shahryar
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authors.lastname: Semnani
authors.forename: Christian C
authors.initials: CC
authors.lastname: Abnet
authors.forename: Paul
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authors.lastname: Brennan
authors.forename: Henrik
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authors.lastname: Møller
authors.forename: Farrokh
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authors.lastname: Saidi
authors.forename: Sanford M
authors.initials: SM
authors.lastname: Dawsey
authors.forename: Reza
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authors.lastname: Malekzadeh
authors.forename: Paolo
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authors.lastname: Boffetta