1. Department of Respiratory Medicine, Peking University International Hospital, Beijing, China
2. Department of Respiratory Medicine, Peking University People's Hospital, Beijing, China
3. Department of Medicine and Center for Sleep and Circadian Neurobiology, University of Pennsylvania, Philadelphia, Pennsylvania
4. PKU-UPenn Sleep Center, Peking University International Hospital, Beijing, China
5. Department of Medicine, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania