Ryota Inokuchi1, Hajime Sato2, Hiromu Maehara3, Masao Iwagami4. 1. Department of General and Emergency Medicine, JR Tokyo General Hospital, Yoyogi, Shibuya-ku, Tokyo, 151-8528, Japan; Department of General and Emergency Medicine, Jujo Hospital, Mangoku 341-1, Kisarazu, Chiba, 292-0003, Japan; Department of Health Policy and Technology Assessment, National Institute of Public Health, 2-3-6 Minami, Wako, Saitama, 351-0197, Japan; Department of Health Services Research, Faculty of Medicine, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki, 305-8575, Japan. Electronic address: intensivecareunits@gmail.com. 2. Department of Health Policy and Technology Assessment, National Institute of Public Health, 2-3-6 Minami, Wako-shi, Saitama, 351-0197, Japan. 3. Department of General and Emergency Medicine, JR Tokyo General Hospital, Yoyogi, Shibuya-ku, Tokyo, 151-8528, Japan. 4. Department of Health Services Research, Faculty of Medicine, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki, 305-8575, Japan; Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street London, WC1E 7HT, UK.