[1] Univ Maryland, Dept Neurol, Baltimore, MD 21201 USA
[2] Univ Maryland, Dept Epidemiol & Prevent Med, Baltimore, MD 21201 USA
[3] Johns Hopkins Univ, Dept Neurol, Baltimore, MD 21218 USA
[4] Johns Hopkins Univ, Dept Med, Baltimore, MD USA
[5] Ctr Dis Control & Prevent, Cardiovasc Hlth Branch, Natl Ctr Chron Dis Prevent & Hlth Promot, Atlanta, GA USA
[6] Ctr Dis Control & Prevent, Natl Ctr Environm Hlth, Div Environm Hlth Lab Sci, Atlanta, GA USA
[7] Emory Univ, Dept Neurol, Atlanta, GA 30322 USA