[1] Duke Univ, Dept Head & Neck Surg & Commun Sci, Sch Med, DUMC Box 3805, Durham, NC 27710 USA
[2] Duke Ctr Study Aging & Human Dev, Durham, NC USA
[3] Duke Univ, Dept Biostat & Bioinformat, Sch Med, Durham, NC 27710 USA
[4] Duke Univ, Dept Med, Div Geriatr, Sch Med, Durham, NC 27710 USA
[5] Duke Univ, Dept Sociol, Durham, NC 27710 USA
[6] Duke Univ, Dept Populat Hlth Sci, Sch Med, Durham, NC 27710 USA