1 Department of Medicine for Integrated Approach to Social Inclusion, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
2 Department of Public Health and Health Policy, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
3 Department of Infectious Diseases, Hiroshima University Hospital, Hiroshima, Japan.
4 Department of Geriatric Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.