[1] Brigham & Womens Hosp, 75 Francis St, Boston, MA 02115 USA
[2] Massachusetts Gen Hosp, Boston, MA 02114 USA
[3] Univ North Carolina Chapel Hill, Chapel Hill, NC USA
[4] Brigham & Womens Hosp, Div Pharmacoepidemiol & Pharmacoecon, 75 Francis St, Boston, MA 02115 USA