1. Department of Neurology, Gangwon Comprehensive Stroke Center, Kangwon National University School of Medicine, Kangwon National University Hospital, Chuncheon, Korea.
2. Center for Preventive Medicine and Public Health, Seoul National University Bundang Hospital, Seongnam, Korea.
3. UIHC Sleep Disorders Center, Clinical Neurology and Psychiatry, The University of Iowa, Iowa, USA.