1. Department of Epidemiology; University of North Carolina at Chapel Hill; Bank of America Center, 137 E. Franklin St, Suite 306 Chapel Hill NC 27514 USA
2. Department of Biostatistics; University of North Carolina at Chapel Hill; Chapel Hill NC USA
3. Department of Medicine; University of North Carolina at Chapel Hill; Chapel Hill NC USA
4. Division of Epidemiology and Community Health; University of Minnesota; Minneapolis MN USA
5. Department of Medicine; University of Mississippi; Jackson MS USA
6. National Heart, Lung, and Blood Institute; Bethesda MD USA
7. Division of Public Health Sciences; Wake Forest University Health Sciences; Winston-Salem NC USA