1. Department of Neurology, Catholic Kwandong University College of Medicine, International St. Mary's Hospital, Incheon, Korea.
2. Sleep Disorders Center, Department of Neurology, Soonchunhyang University College of Medicine, Cheonan Hospital, Cheonan, Korea.
3. Department of Preventive Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.