1. Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore
2. Physical Medicine and Rehabilitation Service, Durham VA Health Care System, Durham, North Carolina
3. Center for Aging and Human Development, Duke University Medical Center, Durham, North Carolina
4. Speech and Audiology, Department of Surgery, Duke University Medical Center
5. Saw Swee Hock School of Public Health, National University of Singapore; and National University Health System
6. Department of Medicine/Geriatrics, Duke University Medical Center; Physical Medicine and Rehabilitation Service, Durham VA Health Care System; and 508 Fulton St, Durham, NC 27705 (USA)