Association between esophageal cancer and drought in China by using Geographic Information System.

The objective of this ecological study was to discover associations between selected climate variables and esophageal cancer (EC) mortality in China using a Geographic Information System (GIS). A digital distribution map of EC mortality in China was established in GIS, which was based on one-tenth of nationwide population cause-of-death surveys conducted in mainland China in 1990-1992. Selected climate variables such as 30-year annual average precipitation and evaporation data of the sample areas were extracted from the environmental databases by zonal statistics finished in Spatial Analyst module of ArcInfo 9.0. Drought Indexes were calculated by using the precipitation and evaporation data and a digital distribution map of them was created to compare with the distribution of EC mortality. Correlation and regression analyses were applied to evaluate associations between the EC mortality rates defined at the sample areas and selected climate variables from the raster datasets. The results of the digital GIS maps of EC mortality and Drought Index show that the high EC mortality mostly occurred in areas with high Drought Index. Correlation and regression analyses also show weak negative correlation between precipitation and EC mortality (p<0.001), and weak positive correlation between Drought Index and EC mortality (p<0.001). This study presented a unique model for the link of cancer and climate using a GIS. The study suggests that drought plays a role in the occurrence and development of EC in China, however, other environmental, biological and genetic factors should not be ignored. There is need for further studies using multiple factors and more accurate and detailed environmental and health data.