1. Spaulding Rehabilitation Hospital; Cambridge Massachusetts
2. School of Public Health; Boston University; Boston Massachusetts
3. Department of Epidemiology; Graduate School of Public Health, University of Pittsburgh; Pittsburgh Pennsylvania
4. Institute of Sports Science and Clinical Biomechanics; University of Southern Denmark; Odense Denmark
5. Laboratory of Epidemiology, Biometry, and Demography; National Institute on Aging; National Institutes of Health; Bethesda Maryland
6. Department of Neurology; School of Medicine; University of Pittsburgh; Pittsburgh Pennsylvania
7. Veterans Affairs Pittsburgh Health Care System; Pittsburgh Pennsylvania
8. Department of Medicine; School of Medicine; University of Pittsburgh; Pittsburgh Pennsylvania
9. Department of Preventive Medicine; University of Tennessee; Memphis Tennessee
10. Division of Gerontology and Geriatric Medicine; Department of Internal Medicine; School of Medicine, Wake Forest; Winston-Salem North Carolina
11. Department of Epidemiology and Biostatistics; University of California at San Francisco; San Francisco California
12. Department of Neurobiology; Eastern Virginia Medical School; Norfolk Virginia
13. Translational Gerontology Branch; National Institute on Aging; National Institutes of Health; Baltimore Maryland