[1] Brown Univ, Sch Med, Rhode Isl Hosp, Div Gen Internal Med, Providence, RI 02903 USA
[2] Harvard Univ, Sch Publ Hlth, Harvard Ctr Risk Anal, Program Econ Evaluat Med Technol, Boston, MA 02115 USA
[3] Harvard Univ, Sch Med, Beth Israel Deaconess Med Ctr, Div Gen Med & Primary Care, Boston, MA 02115 USA
[4] Tufts Univ New England Med Ctr, Hlth Inst, Dept Psychiat, Boston, MA 02111 USA