[1] Michigan State Univ, Dept Neurol, E Lansing, MI 48824 USA
[2] Michigan State Univ, Dept Epidemiol, E Lansing, MI 48824 USA
[3] Univ Calif Riverside, Dept Biostat, Riverside, CA 92521 USA
[4] Univ Calif Los Angeles, Div Gen Internal Med & Hlth Serv Res, Los Angeles, CA USA
[5] Univ Calif Los Angeles, Dept Neurol, Los Angeles, CA 90024 USA