Coffee consumption and risk of prostate cancer: an up-to-date meta-analysis

BACKGROUND/OBJECTIVES: Epidemiologic findings concerning the association between coffee consumption and prostate cancer risk yielded mixed results. We aimed to investigate the association by performing a meta-analysis of all available studies. SUBJECTS/METHODS: We searched PubMed, Web of Science and EMBASE for studies published up to July 2013. We calculated the summary relative risk (RR) and 95% confidence intervals (CIs) for ever, moderate and highest consumption of coffee vs non/lowest consumption. The dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. RESULTS: A total of 12 case-control studies and 12 cohort studies with 42 179 cases were selected for final meta-analysis. No significant associations were found among overall analysis. A borderline positive association was found for highest drinkers in five small hospital-based case-control (HCC) studies involving 2278 cases. However, compared with non/lowest drinkers, the summary RRs were 0.92 (95% CI = 0.85-0.99) for ever drinkers, 0.92 (95% CI = 0.85-1.00) for moderate drinkers and 0.83 (95% CI = 0.72-0.96) for highest drinkers from 12 cohort studies, comprising a total of 34 424 cases. An increase in coffee intake of two cups/day was associated with a 7% decreased risk of prostate cancer according to cohort studies. A significant inverse relationship was also found for fatal prostate cancers and high-grade prostate cancers. CONCLUSIONS: Case-control studies especially HCC ones might be prone to selection bias and recall bias that might have contributed to the conflicting results. Therefore, the present meta-analysis suggests a borderline significant inverse association between coffee consumption and prostate cancer risk based on cohort studies.