In most areas of South China and Southeast Asia, the incidence of esophageal cancer is much lower than that observed in Central China, indicating that there are fewer environmental risk factors and lower susceptibility of esophageal cancer in South China. However, there is still a high incidence area in Southeast China, which might be associated with the highest allele frequency of ALDH2*504Lys in exactly the same geographic area. In contrast to the high incidence of esophageal cancer in Southeast China being the consequence of the high ALDH2*504Lys frequency, it is possible that the high incidence of esophageal cancer in Central China is working to decrease the ALDH2*504Lys frequency while cultural pressure to consume ethanol increases as the impact of *504Lys decreases. The answer depends on which factors increasing risk are most important in which area and how they interact.
