[1] Brown Univ, Dept Epidemiol, Sch Publ Hlth, 121 South Main St,Box G-S-121-4, Providence, RI 02912 USA
[2] Boston Univ, Dept Emergency Med, Sch Med, 771 Albany St,Room 1208, Boston, MA 02118 USA
[3] Brown Univ, Rhode Isl Hosp, Warren Alpert Sch Med, 55 Claverick St, Providence, RI 02903 USA
[4] Boston Univ, Sch Med, Dept Pediat, Div Gen Pediat, 88 East Newton St,Vose Hall Room 322, Boston, MA 02118 USA
[5] Boston Childrens Hosp, Div Adolescent Young Adult Med, Dept Med, 333 Longwood Ave, Boston, MA 02115 USA
[6] Harvard Med Sch, Dept Pediat, 25 Shattuck St, Boston, MA 02115 USA
[7] Univ Massachusetts, Sch Med, Dept Quantitat Hlth Sci, 55 Lake Ave North, Worcester, MA 01605 USA
[8] Univ Massachusetts, Sch Med, Ctr Hlth Policy & Res, 55 Lake Ave North, Worcester, MA 01605 USA