1. Department of Public Health and Health Policy, Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima Japan
2. Department of Community Medicine, Chiba Medical Center, Teikyo University School of Medicine, Ichihara, Chiba, Japan
3. Department of Community Based Medical System, Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan
4. Akimoto Occupational Health Consultant Office, Tokyo Japan