1. Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece
2. Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK
3. Center for Evidence-Based Medicine, Department of Health Services, Policy and Practice, School of Public Health, Brown University, Providence, Rhode Island, USA
4. Division of Gastroenterology, Department of Internal Medicine, Faculty of Medicine, School of Health Sciences, University of Ioannina, Ioannina, Greece