1. School of Medicine, Kangwon National University, Chuncheon, Korea.
2. Department of Neurology, School of Medicine, Kangwon National University, Chuncheon, Korea.
3. Gangwon Comprehensive Stroke Center, Kangwon National University Hospital, Chuncheon, Korea.
4. Department of Cardiology, School of Medicine, Kangwon National University, Chuncheon, Korea.
5. University of Iowa Hospitals and Clinics Sleep Disorders Center, Clinical Neurology and Psychiatry, The University of Iowa, Iowa, IA, USA.