1. Department of Preventive Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
2. Department of Preventive Medicine, Ewha Womans University School of Medicine, Seoul, Korea.
3. Department of Preventive Medicine, School of Medicine, Kyung Hee University, Seoul, Korea.
4. Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
5. Department of Preventive Medicine, University of Ulsan College of Medicine, Seoul, Korea.