[1] Univ Massachusetts, Sch Med, Dept Med, Div Prevent & Behav Med, 55 Lake Ave North, Worcester, MA 01655 USA
[2] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Biostat & Bioinformat Branch, Div Intramural Populat Hlth Res, NIH, Bethesda, MD USA
[3] Ohio State Univ, Coll Publ Hlth, Div Biostat, Columbus, OH 43210 USA
[4] Stanford Univ, Sch Med, Dept Med, Ctr Educ & Res Family & Community Med,Div Gen Med, Palo Alto, CA 94304 USA
[5] Univ Iowa, Carver Coll Med, Iowa City, IA USA
[6] Creighton Univ, Sch Med, Dept Med, Omaha, NE USA
[7] Georgetown Univ Hosp, Dept Med, Washington, DC 20007 USA
[8] Louisiana State Univ Hlth Shreveport, Shreveport, LA USA
[9] Univ Louisville, Sch Med, Louisville, KY 40292 USA
[10] Univ Penn, Perelman Sch Med, Div Pulm Allergy & Crit Care Med, Philadelphia, PA 19104 USA
[11] Univ Minnesota, Sch Med, Dept Family & Community Hlth, Minneapolis, MN 55455 USA
[12] Univ Kentucky, Coll Med, Lexington, KY USA
[13] Univ Alabama Birmingham, UAB Lung Hlth Ctr, Sch Hlth Profess, Clin & Diagnost Sci Dept, Birmingham, AL USA
[14] Harvard Univ, Sch Publ Hlth, Dept Social & Behav Sci, 665 Huntington Ave, Boston, MA 02115 USA