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. 2009 Mar 26:338:b929.
doi: 10.1136/bmj.b929.

Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study

Farhad Islami  1 , Akram Pourshams, Dariush Nasrollahzadeh, Farin Kamangar, Saman Fahimi, Ramin Shakeri, Behnoush Abedi-Ardekani, Shahin Merat, Homayoon Vahedi, Shahryar Semnani, Christian C Abnet, Paul Brennan, Henrik Møller, Farrokh Saidi, Sanford M Dawsey, Reza Malekzadeh, Paolo Boffetta
Affiliations

Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study

Farhad Islami et al. BMJ. .

Abstract

Objective: To investigate the association between tea drinking habits in Golestan province, northern Iran, and risk of oesophageal squamous cell carcinoma.

Design: 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.

Setting: Golestan province, northern Iran, an area with a high incidence of oesophageal squamous cell carcinoma.

Participants: 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.

Main outcome measure: 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).

Conclusion: Drinking hot tea, a habit common in Golestan province, was strongly associated with a higher risk of oesophageal cancer.

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Conflict of interest statement

Competing interests: None declared.

Comment in

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