Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based
case-control study
Farhad Islami, research fellow1,2,3,
Akram Pourshams, associate professor1,
Dariush Nasrollahzadeh, PhD student1,4,
Farin Kamangar, research fellow5,
Saman Fahimi, PhD student 1,6,
Ramin Shakeri, research fellow1,
Behnoush Abedi-Ardekani, pathologist1,
Shahin Merat, associate professor1,
Homayoon Vahedi, associate professor1,
Shahryar Semnani, associate professor and director7,
Christian C Abnet, investigator5,
Paul Brennan, group head2,
Henrik Møller, professor and director3,
Farrokh Saidi, professor1,
Sanford M Dawsey, senior investigator5,
Reza Malekzadeh, professor and director1,
Paolo Boffetta, group head and cluster coordinator2
1 Digestive Disease Research Center, Shariati Hospital, Tehran University of Medical Sciences, 14117 Tehran, Iran,
2 International Agency for Research on Cancer, Lyon, France,
3 King’s College London, Thames Cancer Registry, London,
4 Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden,
5 Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA,
6 Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge,
7 Golestan Research Center of Gastroenterology and Hepatology, Gorgan University of Medical Sciences, Gorgan, Iran
British Medical Journal
26 March (2009); 338:b929.
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°C, 38.9% at 60-64°C, and 22.0% at 65°C or higher. A moderate agreement was found between reported tea drinking temperature and actual temperature measurements (weighted κ 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 κ 0.68).
CONCLUSION: Drinking hot tea, a habit common in Golestan province, was strongly associated with a higher risk of oesophageal cancer.
British Medical Journal
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