Among betel-nut consumers in our cohort, subjects with CD44 polymorphic rs1425802, rs187115, rs713330, rs11821102, rs10836347 and rs13347 genes and who smoked had corresponding 8.004–(95% CI: 1.530–41.854), 13.497–(95% CI: 4.554–40.002), 16.111–(95% CI: 4.359–59.541), 4.228–(95% CI: 1.328–13.463), 4.899–(95% CI: 1.425–16.850), and 14.468-fold (95% CI: 3.778–55.411) higher risks of having oral cancer compared to betel-quid chewers with the WT gene who did not smoke (Table 4). Here, CD44 is linked to lip and oral cavity carcinoma.