[1] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[2] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Hlth Policy & Management, Baltimore, MD USA
[3] Univ Penn, Perelman Sch Med, Philadelphia, PA USA
[4] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA USA
[5] Brown Univ, Sch Publ Hlth, Dept Epidemiol, Providence, RI USA
[6] Univ Calif San Francisco, Dept Med, San Francisco, CA USA
[7] Brown Univ, Dept Med, Providence, RI USA