Division of Cardiovascular Medicine, Department of Medicine and Department of Sleep and Circadian Cardiology, Jichi Medical University School of Medicine, Shimotsuke, Tochigi, Japan. kkario@jichi.ac.jp. Division of Cardiovascular Medicine, Department of Medicine and Department of Sleep and Circadian Cardiology, Jichi Medical University School of Medicine, Shimotsuke, Tochigi, Japan. Uchiyama Clinic, Niigata, Japan. Onga Nakama Medical Association Onga Hospital, Fukuoka, Japan. National Center for Global Health and Medicine, Tokyo, Japan. Noshiro Clinic, Tochigi, Japan. Japanese Red Cross Koga Hospital, Ibaraki, Japan.