1. From the Departments of Neurology (S.N.P., S.C.J., M.N.N.-H.) and Epidemiology and Biostatistics (S.C.J.), University of California, San Francisco, Calif; the Division of Research (S.S.), Kaiser Permanente-Northern California, Oakland, Calif; and the Northern California Kaiser Permanente Medical Care Plan (J.G.K.), Oakland, Calif.