MAOA and pharynx cancer: Compared to non-BQ chewers with MAOA rs5906957 (G-allele), BQ chewers with MAOA rs5906957 (A-allele) had a significantly synergistic risk of oral and pharyngeal cancers (AOR = 24.15; 95% CI, 10.44–55.89) and risk of OPMD (AOR = 10.04; 95% CI, 2.83–35.56).