1. Department of Public Health, Dokkyo Medical University School of Medicine, Tochigi-ken, Japan
2. Ibaraki Prefectural Health Plaza, Ibaraki-ken, Japan
3. Public Health, Department of Social and Environmental Medicine, Osaka University Graduate School of Medicine, Osaka-fu, Japan
4. Department of Health and Welfare, Ibaraki Prefectural Office, Ibaraki-ken, Japan