[1] Massachusetts Gen Hosp, Dept Anesthesia Crit Care & Pain Med, 55 Fruit St, Boston, MA 02114 USA
[2] Massachusetts Gen Hosp, Dept Neurol, Boston, MA 02114 USA
[3] Duke Clin Res Inst, Clin Trials Stat Grp, Durham, NC USA
[4] Duke Clin Res Inst, Outcomes Res & Assessment Grp, Durham, NC USA
[5] Univ Calgary, Dept Clin Neurosci, Calgary, AB, Canada
[6] Univ Calgary, Hotchkiss Brain Inst, Calgary, AB, Canada
[7] Univ Calif Los Angeles, Med Ctr, Ahmanson, Dept Med,Cardiomyopathy Ctr, Los Angeles, CA 90024 USA
[8] Ctr Dis Control & Prevent, Natl Ctr Chron Dis Prevent & Hlth Promot, Div Reprod Hlth, Atlanta, GA USA
[9] Ctr Dis Control & Prevent, Div Heart Dis & Stroke Prevent, Atlanta, GA USA