As for the effect modification by alcohol habits, drinking subjects carrying the variant allele of CYP2E1 (*5A or *6 alleles) had an OR of 3.70 (95%CI: 1.45–9.37) of gastric cancer compared to those drinking without the variant allele, with the result of the heterogeneity test among the strata showing a significant effect modification by alcohol (p value = 0.001, Table 3). Here, CYP2E1 is linked to gastric cancer.