1. Clinical Investigator Program, Department of Medicine, University of British Columbia, Vancouver, BC, Canada V5Z 1M9
2. Division of Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego, La Jolla, CA 92037, USA
3. Department of Otorhinolaryngology-Head and Neck Surgery, Sleep Medicine Center, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China