Objectives: To determine whether tea consumption and intake of other beverages increases bladder cancer risk.
Methods: A case-control study was conducted in Kaohsiung, Taiwan between August 1996 and June 1997. Index patients studied were consecutive patients with histologically confirmed, newly diagnosed bladder cancer in two major hospitals. For each patient, 4 controls were selected from patients with non-neoplastic and nonurologic diseases undergoing surgical operations in the same hospital and individually matched by sex, age, and date of admission. Using a structured questionnaire, a trained interviewer interviewed 40 patients and 160 controls. Conditional logistic regression analysis adjusting for ethnicity, family history, and smoking status and matching variables were used to estimate the odds ratio (OR) and 95% confidence interval (CI).
Results: Tea consumption overall was associated with increased bladder cancer risk (OR 3.29, 95% CI 1.34 to 8.05). Compared with non-tea drinkers, the odds ratios of bladder cancer for oolong tea drinkers was 3.00 (95% CI 1.20 to 7.47); for non-oolong tea drinkers (black and/or other green tea), it was 14.86 (95% CI 2.13 to 103.83). The risk was greater among those who began to drink tea before age 40 (OR 9.50, 95% CI 2.39 to 37.75) and those who had been drinking tea for more than 30 years (OR 17.75, 95% CI 3.00 to 105.17). Coffee, tap water, and alcohol consumption were associated with a slightly increased risk, and both soy juice and rice juice consumption were associated with reduced risk; none of these odds ratio estimates were statistically significant, however.
Conclusions: Our results suggest that tea consumption is associated with an increased risk of bladder cancer.