Coffee, Tea, Cola, and Bladder Cancer Risk: Dose and Time Relationships

Objective To further analyze the relation between coffee, tea, and energy drinks and bladder cancer risk, considering dose, duration, and other time-related factors. Methods and Results A multicentric case-control study on 690 bladder cancer cases and 665 hospital controls was conducted in Italy between 2003 and 2014. Odds ratios (ORs) for bladder cancer were estimated using multiple logistic regression models. Sex-, age-, and tobacco-adjusted ORs were 1.27 (95% confidence interval [CI] 0.84-1.94) for current drinkers and 1.69 (95% CI 1.05-2.72) for lifetime drinkers of ≥4 cups/day, compared with non- or occasional coffee drinkers. The corresponding ORs for an increment of 1 cup/day were 1.03 (95% CI 0.96-1.11) and 1.07 (95% CI 0.99-1.15). No association was found between bladder cancer risk and duration or age at starting, and no significant heterogeneity was found according to age and sex, although a slight increased risk emerged in never smokers. Decaffeinated coffee, tea, cola, and energy drinks were not related with bladder cancer risk. Conclusion Our study found no significant relation between coffee and bladder cancer risk after accounting for smoking, although the OR was above unity for high lifetime habit. The lack of dose and duration relationships, however, suggests the absence of a causal relation.