1. Department of Otorhinolaryngology/Head and Neck Surgery University Medical Center Groningen University of Groningen Groningen The Netherlands
2. Department of Anaesthesiology University Medical Center Groningen University of Groningen The Netherlands
3. Department of Otorhinolaryngology Amsterdam University Medical Center University of Amsterdam The Netherlands
4. Department of Research Netherlands Comprehensive Cancer Organisation (IKNL) Utrecht The Netherlands
5. Department of Epidemiology University Medical Center Groningen University of Groningen Groningen The Netherlands