1. Pulmonary Division, the First Hospital of Jilin University, Changchun, Jilin, China
2. Division of Sleep Medicine, Department of Medicine, University of Pennsylvania; Philadelphia, PA
3. Department of Biostatistics, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA
4. Sleep Center, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, PA