1. Department of Neurology, National Health Insurance Service Ilsan Hospital, Goyang, Korea
2. Health Insurance Research Institute, National Health Insurance Service, Wonju, Korea
3. Division of Rheumatology, Department of Internal Medicine, National Health Insurance Service Ilsan Hospital, Goyang, Korea
4. Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea
5. Biostatistics Collaboration Unit, Department of Biomedical Systems Informatics, Yonsei University College of Medicine, Seoul, Korea