Application of Bayesian Multilevel Space-Time Models to Study Relative Risk of Esophageal Cancer in Iran 2005-2007 at a County Level


Background: Reported age standardized incidence rates for esophageal cancer in Iran are 0.88 and 6.15 forfemales and males, at fifth and the eighth ranks, respectively, of cancers overall. The present study aimed to maprelative risk using more realistic and less problematic methods than common estimators. Materials and
Methods:In this ecological investigation, the studied population consisted of all esophageal cancer patients in Iran from2005 to 2007. The Bayesian multilevel space-time model with three levels of county, province, and time was usedto measure the relative risk of esophageal cancer. Analyses were conducted using R package INLA.
Results: Thetotal number of registered patients was 7,160. According to the results, the three-level model with adjustmentfor risk factors of physical activity and smoking had the best fit among all models .The overall temporal trendwas significantly increasing. At county level, Ahar, Marand, Salmas, Bojnoord, Saghez, Sarakhs, Shahroud andTorbatejam had the highest relative risks. Physical activity was found to have significant direct association withrisk of developing esophageal cancer.
Conclusions: Given to great variation across geographical areas, manydifferent factors affect the incidence of esophageal cancer. Conducting further studies at the individual level inareas with high incidence could provide more detailed information on risk factors of esophageal cancer.