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Coffee, tea and urinary tract cancer

 

Coffee and tea are two of the most popular beverages consumed and so any potential relationship with disease or illness is important. This meta-analysis examines the relationship between coffee and tea consumption and urinary tract cancer.

Message

Coffee consumption increases urinary tract cancer by approximately 20%. There is no association between tea consumption and urinary tract cancer.

Reference

MPA Zeegers et al. Are coffee and tea consumption associated with urinary tract cancer risk? A systematic review and meta-analysis. International Journal of Epidemiology 2001 30: 353-362.

Search

The literature was searched using MEDLINE, Cancerlit and Current Contents until 2000. All languages were included and bibliographies of identified papers were then reviewed. To be included, papers had to provide sufficient information to perform a summary odds ratio.

Thirty-four case-control studies and three cohort studies were identified. The majority of case-control studies were either population-based (12) or hospital-based (18). Information on tea and coffee consumption was obtained by interview in the majority of studies, with a few (five) using questionnaires. All but three studies either included all neoplasms of the urinary tract as cases (of which more than 90% were found to involve bladder cancer) or selected bladder carcinomas only. Most studies used histologically confirmed cases with urothelial cell cancer.

Results

Coffee

Compared with no coffee consumption, current consumption was associated with an 18% increased risk of bladder cancer in 14 studies with men and women combined (odds ratio 1.18, 95% confidence interval 1.01 to 1.38). These, and subsequent results, were adjusted for age and smoking.

In 16 studies with men the increased risk among current coffee drinkers was 26% (odds ratio 1.26, 95% confidence interval 1.09 to 1.46). There was no increased risk among women in 12 studies (odds ratio 1.08, 95% confidence interval 0.79 to 1.46).

There was no association between decaffeinated coffee consumption and bladder cancer.

Tea

There was no association between tea consumption and bladder cancer in seven studies with men only (odds ratio 1.08, 95% confidence interval 0.94 to 1.24), six studies with women only (odds ratio 0.99, 95% confidence interval 0.81 to 1.20) or seven studies with men and women combined (odds ratio 1.01, 95% confidence interval 0.92 to 1.10).

Comment

Although no association was found between coffee consumption in women and bladder cancer, the quality of papers contributing to this result is largely unknown and unfortunately this meta-analysis did not specify how many participants contributed to any of its analyses. For these reasons, it would make more sense to use the results for men and women combined.

It is a shame that there was not enough information in the individual papers to be able to quantify the amount of coffee associated with a 20% increased risk of bladder cancer. One can only assume that a moderate amount is acceptable, but if there is a history of urinary tract cancer, be careful.