Are coffee and tea consumption associated with urinary tract cancer risk? A systematic review and meta-analysis

Background Narrative reviews have concluded that there is a small associati on between coffee consumption and an increased risk of urinary tract cancer , possibly due to confounding by smoking. No association for tea consumptio n has been indicated. This systematic review attempts to summarize and quan tify these associations both unadjusted and adjusted for age, smoking and s ex. Methods Thirty-four case-control and three follow-up studies were included in this systematic review. Summary odds ratios (OR) were calculated by meta -regression analyses. Results The unadjusted summary OR indicated a small increased risk of urina ry tract cancer for current coffee consumers versus non-drinkers. The adjus ted summary OR were: 1.26 (95% CI : 1.09-1.46) for studies with only men, 1 .08 (95% CI:0.79-1.46) for studies with only women and 1.18 (95% CI: 1.01-1 .38) for studies with men and women combined. Neither unadjusted nor adjust ed summary OR provided evidence for a positive association between tea cons umption and urinary tract cancer. Even though studies differed in methodolo gy, the results were rather consistent. We did not perform dose-response an alyses for coffee and tea consumption due to sparse data. Conclusions In accordance with earlier reviews, we found that coffee consum ption increases the risk of urinary tract cancer by approximately 20%. The consumption of tea seems not to be related to an increased risk of urinary tract cancer.