1. Harborview Medical Center, Department of Rehabilitation Medicine, University of Washington, 325 Ninth Avenue, Seattle, WA 98104, USA
2. Department of Rehabilitation Medicine, University of Washington, Seattle, WA 98195, USA
3. School of Nursing, University of Washington, Seattle, WA 98195, USA
4. School of Public Health, University of Washington, Seattle, WA 98195, USA
5. Coordinating Center, CDC Healthy Aging Research Network, University of Washington, Seattle, WA 98195, USA