1 Department of Medicine, Samsung Medical CenterSungkyunkwan University School of MedicineSeoulSouth Korea.
2 Department of Clinical Research Design and Evaluation, Samsung Advanced Institute for Health Sciences and TechnologySungkyunkwan UniversitySeoulSouth Korea.
3 Center for Clinical Epidemiology, Samsung Medical CenterSungkyunkwan UniversitySeoulSouth Korea.
4 Department of Epidemiology, Welch Center for Prevention, Epidemiology and Clinical ResearchJohns Hopkins Medical InstitutionsBaltimoreMarylandUSA.