1. Gastroenterology and Hepatology Unit, Division of Internal Medicine, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand
2. Nanthana-Kriangkrai Chotiwattanaphan Institute of Gastroenterology and Hepatology, Songklanagarind Hospital, Hat Yai, Songkhla, Thailand
3. School of Public Health, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand
4. Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand