[1] Vrije Univ Amsterdam Med Ctr, EMGO Inst Hlth & Care Res, Dept Publ & Occupat Hlth, NL-1081 BT Amsterdam, Netherlands
[2] Brigham & Womens Hosp, Div Gen Med, Boston, MA 02115 USA
[3] Harvard Univ, Sch Med, Boston, MA USA
[4] Michael E DeBakey VA Med Ctr, Houston VA Hlth Serv Res & Dev Ctr Excellence, Houston, TX USA
[5] Baylor Coll Med, Dept Med, Sect Hlth Serv Res, Houston, TX 77030 USA