[1] Univ North Carolina Chapel Hill, Dept Hlth Behav, Gillings Sch Global Publ Hlth, Chapel Hill, NC USA
[2] Univ North Carolina Chapel Hill, Carolina Populat Ctr, Chapel Hill, NC USA
[3] Univ North Carolina Chapel Hill, Dept Epidemiol, Gillings Sch Global Publ Hlth, Chapel Hill, NC USA
[4] Duke Univ, Dept Community & Family Med, Sch Med, Durham, NC USA