1. Department of Otorhinolaryngology; Head and Neck Surgery; Maastricht University Medical Center; Maastricht The Netherlands
2. Department of Epidemiology; Maastricht University; Maastricht The Netherlands
3. Department of Gastroenterology; Radboud University Nijmegen Medical Center; Nijmegen The Netherlands
4. Department of Surgery; Maastricht University Medical Center; Maastricht The Netherlands