1. From the Departments of Epidemiology (C.R., N.W., A.B.N., Y.D., E.B.-M., K.S.-T.), Neurological Surgery (Y.C.), Psychiatry (H.J.A), and Bioengineering (V.V.), University of Pittsburgh, Pittsburgh, PA; and the Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, Bethesda, MD (T.B.M.).