[1] Cornell Univ, Med Ctr, Dept Med, New York, NY 10021 USA
[2] Wake Forest Univ, Dept Med, Winston Salem, NC 27109 USA
[3] Univ Alabama Birmingham, Dept Prevent Med, Birmingham, AL 35294 USA
[4] Univ Utah, Sch Med, Dept Med, Salt Lake City, UT 84112 USA
[5] Washington Univ, Dept Biostat, St Louis, MO 63130 USA
[6] Univ Minnesota, Dept Epidemiol, Minneapolis, MN 55455 USA