CHRNA5 and nasopharyngeal carcinoma: Similarly, the difference in the CHRNA5 ins/ins, ins/del, and del/del genotype distributions between the NPC cases and controls were statistically significant (χ2 = 7.762, P = 0.021) and the ins/del heterozygote was more common among the NPC cases than among the controls, the difference were statistically significant (χ2 = 7.676, P = 0.006).