ABSTRACT
A total of 7,359 residents in northeastern arseniasisendemic areas in Taiwan were followed from 1998 to 2009. The disease status of each subject was ascertained through linkage with computerized Taiwan National Health Insurance (NHI) database. In Taiwan, 96.3% of residents were insured for NHI in the first three years when the insurance system was implemented and 99% of residents were insured at the end of 2008. The data including complete outpatients visits, emergency visits, hospital admissions, prescriptions, disease and vital status during the study period were used in this study. Identification of patients was defined by the presence of ICD ninth revision, clinical modification (ICD-9-CM) of 444.0-444.9 for arterial embolism and thrombosis. Cox regression analysis was used to determine the hazard ratio of the disease associated with arsenic concentration in well water.
