[1] Univ N Carolina, Dept Epidemiol, Chapel Hill, NC 27514 USA
[2] Ctr Dis Control & Prevent, Atlanta, GA USA
[3] Univ N Carolina, Dept Hlth Policy & Management, Chapel Hill, NC 27514 USA
[4] Wake Forest Univ, Div Publ Hlth Sci, Winston Salem, NC 27109 USA
[5] Univ N Carolina, Dept Biostat, Chapel Hill, NC 27514 USA