1. From the Division of Epidemiology & Community Health (J.D.S., A.R.F.), School of Public Health, University of Minnesota, Minneapolis; the Departments of Neurology and Epidemiology (W.T.L.), University of Washington, Seattle; the Division of Epidemiology and Biostatistics (E.S.), University of Arizona, Tucson; the Department of Epidemiology (W.D.R.), University of North Carolina, Chapel Hill; the Departments of Medicine and Pathology (M.C.), University of Vermont, Burlington.