[1] Tsinghua Univ, Sch Publ Policy & Management, Beijing, Peoples R China
[2] Boston Childrens Hosp, Dept Neurol & ICCTR Biostat, Boston, MA USA
[3] Boston Childrens Hosp, ICCTR Biostat & Res Design Ctr, Boston, MA USA
[4] Harvard Med Sch, Boston, MA USA
[5] Peking Univ, Sch Publ Hlth, Beijing, Peoples R China