Authors: Farhad Islami, 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

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

Conclusion: and policy implications: Our results showed a noticeable increase in risk of oesophageal squamous cell carcinoma associated with drinking tea hot. A large proportion of Golestan inhabitants drink hot tea, so this habit may account for a substantial proportion of the cases of oesophageal cancer in this population. Informing the population about the hazards of drinking hot tea may be helpful in reducing the incidence of oesophageal cancer in Golestan and in other high risk populations where similar habits are prevalent.