1. From the Physical Therapy Program (D.S.-L.), School of Allied Medical Professions, The Ohio State University, Columbus, Ohio; the School of Nursing (P.C.C.) and the Department of Rehabilitation Medicine (A.G., S.B.), Emory University, Atlanta, Ga; and the Division of Biostatistics (A.Z.), Washington University, St Louis, Mo. Current address for A.G. is Centers for Disease Control and Prevention, Atlanta, Ga.