1. Department of Neurology, Keimyung University School of Medicine, Dongsan Medical Center, Daegu, South Korea
2. Department of Neurology, School of Medicine, Soonchunhyang University, Bucheon, South Korea
3. Department of Biostatistics, Bioinformatics, and Biomathematics, Georgetown University, Washington, DC
4. Department of Neurology, Georgetown University Hospital, Washington, DC
5. Sleep Disorders Center, Department of Neurology, Soonchunhyang University College of Medicine, Cheonan Hospital, Cheonan, South Korea