1. Department Respiratory Diseases and Sleep Disorders Centre, AZ Delta , Rumbeke , Belgium
2. Department Internal Medicine and Paediatrics, Faculty of Medicine and Health Sciences, Ghent University , Gent , Belgium
3. Reykjavik University Sleep Institute, School of Technology, Reykjavik University , Reykjavik , Iceland
4. Internal Medicine Services, Landspitali – The National University Hospital of Iceland , Reykjavik , Iceland