Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control studyBMJ 2009; 338 doi: http://dx.doi.org/10.1136/bmj.b929 (Published 27 March 2009) Cite this as: BMJ 2009;338:b929
- Farhad Islami, research fellow123,
- Akram Pourshams, associate professor1,
- Dariush Nasrollahzadeh, PhD student14,
- Farin Kamangar, research fellow5,
- Saman Fahimi, PhD student16,
- 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
- 1Digestive Disease Research Center, Shariati Hospital, Tehran University of Medical Sciences, 14117 Tehran, Iran
- 2International Agency for Research on Cancer, Lyon, France
- 3King’s College London, Thames Cancer Registry, London
- 4Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
- 5Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA
- 6Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge
- 7Golestan Research Center of Gastroenterology and Hepatology, Gorgan University of Medical Sciences, Gorgan, Iran
- Correspondence to: R Malekzadeh or P Boffetta
- Accepted 18 December 2008
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.
We thank the staff of the Atrak Clinic, including Karim Aghcheli, Noushin Taghavi, Haji-Amin Marjani, Rabaeh Rajabzadeh, Monireh Badakhshan, Bita Mohammadi, Halimeh Eskandarnejhad, Safora Kor, Soleiman Kasalkheh, and Ashor Yolmeh; Noorli Radgohar, Abdolazim Khozeini, Rahmat Ghaziani, Mohammad Hasan Brazandeh, Abdolhakim Ebadati, Naser Keramat, and Ahmad Nosrati for their valuable help; the local health networks and health workers (Behvarzes) in the study area for their assistance in recruitment of controls; the Iranian Social Security Organization for their local support; and the Golestan Cohort Study Center staff for their dedicated work.
Contributors: FI, AP, DN, FK, SF, RS, BA-A, SM, HV, CCA, PBren, FS, SMD, RM, and PBoff designed and implemented the study. FI, AP, DN, SF, RS, BA-A, SM, HV, SS, FS, and RM acquired the data. FI analysed the data. FI, PBoff, FK, SD, HM, and RM interpreted the data. FI, FK, and PBoff drafted the manuscript. All authors reviewed the manuscript and approved the final version to be published.
Funding: This study was supported by the Digestive Disease Research Center of Tehran University of Medical Sciences (grant No 82-603), by an intramural programme of the National Cancer Institute, National Institutes of Health, and by the International Agency for Research on Cancer. The funding sources had no role in the design, conduct, statistical analysis and interpretation of results, or writing of the manuscript.
Competing interests: None declared.
Ethical approval: The case-control study was reviewed and approved by the institutional review boards of the Digestive Disease Research Center (DDRC) of Tehran University of Medical Sciences and the US National Cancer Institute. Both cases and controls gave written informed consent for the interview. The conduct of Golestan Cohort Study was reviewed and approved by the institutional review boards of DDRC, the International Agency for Research on Cancer, and the US National Cancer Institute.
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