Mortality risks of oesophageal cancer associated with hot tea, alcohol, tobacco and diet in Japan.

To clarify mortality risks of oesophageal cancer associated with hot tea, alcohol, tobacco and diet, further analyses on the data from a large prospective cohort study in Japan were conducted. The subjects for analysis were 220,272 men and women aged 40 to 69 at the baseline of 1965. There were 440 oesophageal cancer deaths during the period from January 1966 to December 1981. Person-years at risk were 3,065,182 in total. Rate ratio and 95% confidence interval adjusted for attained age, prefecture, occupation and sex were (RR (95% CI)): 1.6 (1.2-2.0) for hot tea (drinking green tea at high temperatures) in comparison with not-hot tea (drinking green tea at moderate temperatures); 2.4 (1.8-3.1) for daily (4 times/week or more) alcohol drinking in comparison with non-drinking; and 2.3 (1.7-3.1) for heavy smoking (15 cigarettes/day or more) in comparison with non-smoking. Dose-response relationships were found in alcohol drinking and smoking among men and women (p for trend; p < 0.001). The rate ratios were not significantly associated with the dietary factors except for green-yellow vegetables (1-3 times/month or less in comparison with daily; RR = 2.0, 95% CI: 1.2-3.1), where a no dose-response trend was observed (p = 0.45). In comparison based on the binary variables, the RR for the subjects with daily alcohol drinking and current smoking was 3.9 with 95% CI of 2.7 to 5.4, relative to those exposed to neither habit. The joint effect of alcohol drinking (A) and smoking (S) was more than additive (A*S > A + S: 3.9 > 1 + (1.0-1) + (1.6-1)). Further sub-analysis showed that the RR for the subjects with daily alcohol drinking, current smoking and hot tea was 5.7 with 95% CI of 3.7 to 8.9, when the reference was the subjects with not-daily alcohol drinking, non-smoking and not-hot tea. Similar results were obtained from further adjustment of green-yellow vegetables. It is concluded that mortality risks of oesophageal cancer in the present cohort were substantially associated with thermal effect of hot tea, alcohol drinking, smoking and lower consumption of green-yellow vegetables. This finding suggests that life-style modification for smoking and dietary habits is essential to reduce the risks of oesophageal cancer in Japan.