[1] Univ N Carolina, Dept Epidemiol, Gillings Sch Global Publ Hlth, Chapel Hill, NC 27515 USA
[2] Univ N Carolina, Dept Biostat, Gillings Sch Global Publ Hlth, Chapel Hill, NC 27515 USA
[3] Univ N Carolina, Inst Res & Assessment, Chapel Hill, NC 27515 USA
[4] Univ N Carolina, Peers Progress, Gillings Sch Global Publ Hlth, Chapel Hill, NC 27515 USA
[5] Univ N Carolina, Dept Hlth Behav, Gillings Sch Global Publ Hlth, Chapel Hill, NC 27515 USA