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

Abstract

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.

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

“…A pooled RR of 0.90 (95% CI ¼ 0.84-0.97) was observed when reanalyzing the data coming from the cohort studies using a random-effects model. This estimate suggests a weaker inverse association between coffee consumption and PCa risk as compared with what observed by Zhong et al 1…”

“…The meta-analysis on prostate cancer mortality suffers from the same issue: in our study, the crude RR for high coffee drinkers (X6 cups per day) compared with nondrinkers (RR ¼ 0.36 (95% CI ¼ 0.20-0.64)) was very different from the multivariable-adjusted RR calculated, for example, using the Hamling method from the published results (RR ¼ 0.71 (95% CI ¼ 0.40-1.25)). Again, the pooled RR form a random-effects model suggested a weaker association between coffee consumption and fatal PCa (RR ¼ 0.71 (95% CI ¼ 0.54-0.94)) as compared with what observed by Zhong et al 1 (RR ¼ 0.61 (95% CI ¼ 0.42-0.90)). A 29% reduction in PCa mortality when comparing the highest with the lowest coffee consumption category (mean range ¼ 8 cups per day) is consistent with a RR of 0.89 for every three cups per day increase in coffee consumption that we observed in a recent dose-response meta-analysis 7 (exp(ln(0.89)/3*8) ¼ 0.73).…”

“…Furthermore, they observed, from a doseresponse meta-analysis, a 7% decreased risk of PCa for every two cups per day increase in coffee consumption (RR ¼ 0.93 (95% CI ¼ 0.88-0.99)). The authors also graphically presented that result in Figure 3b 1 . In the present letter, we would like to discuss two issues of that meta-analysis that we hope might draw attention to two fundamental steps of a meta-analysis: collection of the data and presentation of the results.…”

“…In their recent meta-analysis, Zhong et al 1 reported a 17% reduction in prostate cancer (PCa) risk when comparing highest versus non/lowest coffee consumption categories among 12 cohort studies 1 (relative risk (RR) ¼ 0.83 (95% confidence interval (CI) ¼ 0.72-0.96)). Furthermore, they observed, from a doseresponse meta-analysis, a 7% decreased risk of PCa for every two cups per day increase in coffee consumption (RR ¼ 0.93 (95% CI ¼ 0.88-0.99)).…”

“…First, Zhong et al 1 used in their meta-analysis crude RRs extracted from our cohort study 2 instead of multivariable-adjusted RRs, as incorrectly reported in Table 1. 1 For example, they reported a RR of 0.52 (95% CI ¼ 0.41-0.65) and of 0.55 (95% CI ¼ 0.36-0.86) for localized and advanced PCa respectively, comparing men who drank six or more cups per day with nondrinkers. In our study the risk of PCa increased exponentially with age and older men tended to drink less coffee.…”