1. Department of Otolaryngology–Head and Neck Surgery University of Ottawa Ottawa Ontario Canada
2. Ottawa Hospital Research Institute Ottawa Ontario Canada
3. Department of Epidemiology Erasmus Medical Centre Rotterdam the Netherlands
4. Department of Neurosurgery Brigham and Women's Hospital, Harvard Medical School Boston Massachusetts U.S.A
5. School of Epidemiology and Public Health, University of Ottawa Ottawa Ontario Canada
6. Institute for Clinical and Evaluative Sciences Toronto Ontario Canada
7. Department of Medicine, Division of Hematology University of Ottawa Ottawa Ontario Canada
8. Department of Medicine, Division of Respirology University Health Network Toronto Ontario Canada