1. Department of Hygiene, Hirosaki University School of Medicine, Hirosaki, Japan
2. First Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan
3. Department of Health, Hirosaki University School of Health Sciences, Hirosaki, Japan
4. Department of Food Hygiene, Division of Food Science and Technology, Nippon Veterinary and Animal Science University, Tokyo, Japan