[1] Beth Israel Deaconess Med Ctr, Dept Neurol, 330 Brookline Ave, Boston, MA 02215 USA
[2] Boston Univ, Sch Med, Dept Biostat, Boston, MA 02215 USA
[3] Boston Univ, Sch Med, Dept Neurol, Boston, MA 02215 USA
[4] Univ Calif Davis, Dept Neurol, Davis, CA 95616 USA
[5] Framingham Heart Dis Epidemiol Study, Framingham, MA USA