1. Total Healthcare Center, Kangbuk Samsung Hospital, School of Medicine, Sungkyunkwan University, Seoul, Korea.
2. Center for Cohort Studies, Total Healthcare Center, Kangbuk Samsung Hospital, School of Medicine, Sungkyunkwan University, Seoul, Korea.
3. Department of Preventive Medicine, School of Medicine, Kyung Hee University, Seoul, Korea.
4. Department of Neurology, Kangbuk Samsung Hospital, School of Medicine, Sungkyunkwan University, Seoul, Korea.
5. Department of Occupational and Environmental Medicine, School of Medicine, Kyung Hee University, Seoul, Korea.