[1] Univ Pittsburgh, Sch Publ Hlth, Epidemiol Data Ctr, Dept Epidemiol, Pittsburgh, PA 15261 USA
[2] Univ Maryland, Sch Med, Baltimore, MD 21201 USA
[3] Boston Univ, Med Ctr, Boston, MA 02215 USA
[4] Mayo Clin & Mayo Fdn, Rochester, MN 55905 USA
[5] Emory Univ Hosp, Atlanta, GA 30322 USA
[6] Univ Penn, Ctr Med, Philadelphia, PA 19104 USA
[7] Brown Univ, Rhode Isl Hosp, Providence, RI 02903 USA