1. From the Department of Epidemiology (S.A.J., W.D.R.) and Department of Biostatistics (L.W.), Gillings School of Global Public Health, University of North Carolina at Chapel Hill; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD (R.F.G.); and Epidemiology and Biostatistics Division, the University of Arizona College of Public Health, Tucson (E.S.).