[1] Wake Forest Univ, Sch Med, Winston Salem, NC 27157 USA
[2] Wake Forest Univ, Sch Med, Dept Epidemiol & Prevent, Winston Salem, NC 27157 USA
[3] Wake Forest Univ, Sch Med, Dept Pediat, Med Ctr Blvd, Winston Salem, NC 27157 USA
[4] Wake Forest Univ, Sch Med, Dept Biostat, Winston Salem, NC 27157 USA