1. Department of Neurology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea
2. Department of Neurology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Korea
3. Statistics and Data Center, Samsung Medical Center, Seoul, Korea
4. Department of Neurology, Dong-A University College of Medicine, Dong-A University Medical Center, Busan, Korea
5. Department of Nuclear Medicine, Dong-A University College of Medicine, Dong-A University Medical Center, Busan, Korea
6. Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea
7. Department of Neurology, Yonsei University School of Medicine, Severance hospital, Seoul, Korea
8. Department of Neurology, Kyung Hee University Hospital, Seoul, Korea
9. Department of Neurology, Kangwon National University College of Medicine, Chuncheon-si, Gangwon-do, Korea
10. Department of Internal Medicine, Division of Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA