Heredity, diet and lifestyle as determining risk factors for the esophageal cancer on Nanao Island in Southern China.

In this case-control study we evaluated contribution of environmental and genetic factors for risk of esophageal cancer (EC) by studying populations on Nanao Island (highest risk area for EC in China) and Shanwei (low risk region). Data on lifestyle, diet and family history were collected from the 166 newly diagnosed EC patients on Nanao between 2003 and 2004, from their 1450 first degree relatives and from controls on Nanao and Shanwei. Univariate and logistic regression analysis, family aggregation patterns, standardized incidence ratio (SIR), segregation ratio and heritability index were evaluated. The family cancer history was a significant risk factor for the two scenarios; Nanao cases versus Nanao controls, and Nanao controls versus Shanwei controls. Other risk factors included smoking, alcohol and fermented fish sauce. After adjusting for confounding variables, family history was independently associated with the occurrence of EC in Nanao cases versus Nanao controls. The incidence in the first degree relatives of Nanao cases was 0.86%, significantly higher than that of the public (0.12%) and SIR value was 1.44 in the first degree relatives of the 166 EC cases. The segregation ratio was 0.11 and the heritability index among first degree relatives was 40%. Our study indicates that there are steady pathogenic risk factors in the Nanao population's lifestyle but genetic factors also play an important role for EC onset.