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

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


Islami F, Pourshams A, Nasrollahzadeh D, Kamangar F, Fahimi S, Shakeri R, Abedi-Ardekani B, Merat S, Vahedi H, Semnani S, Abnet CC, Brennan P, Møller H, Saidi F, Dawsey SM, Malekzadeh R, Boffetta P.

Digestive Disease Research Center, Shariati Hospital, Tehran University of Medical Sciences, 14117 Tehran, Iran.

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.