1. Department of Physical Medicine and Rehabilitation, National Health Insurance Service Ilsan Hospital, Goyang, Korea.
2. Department of Rehabilitation Medicine and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Statistics, Korea University, Seoul, Korea.
4. Department of Physical Medicine and Rehabilitation, Inje University Ilsanpaik Hospital, Goyang, Korea.
5. Yonsei University College of Medicine, Seoul, Korea.