A systematic review reported that coffee consumption would decrease risk of colon cancer in Asian women. But the systematic review arises the issue of duplication, so that a meta-epidemiological study was conducted.
The selection criteria were defined that a prospective cohort follow-up study conducted to evaluate coffee consumption and risk of colon cancer in Asian and showed adjusted relative risk and its 95% confidence interval. In order to conduct meta-analysis, the highest versus lowest method was applied to extract relative risk and its 95% confidence intervals of the highest category. Random effect model was applied if I-squared value was over 50%.
After avoiding duplication, 9 cohort data were selected for meta-analysis. The summary relative risk (and their 95% confidence intervals) [I-square value] were 0.90 (95% CI: 0.79-1.03) [0.0%] in men, and 0.64 (95% CI: 0.36-1.15) [65.9%] in women, respectively.
The results suggest that coffee consumption is not associated with the risk of colon cancer in Asian men and women. The findings of this study are consistent with the results of two systematic reviews conducted under the same hypothesis and selection criteria. Additional epidemiological studies are needed for the inflection of colon cancer risk as the dose of coffee increases and the difference in the protective effect by sex.