1. Department of Epidemiology; University of North Carolina; Chapel Hill North Carolina USA
2. Department of Sociology; University of North Carolina; Chapel Hill North Carolina USA
3. Carolina Population Center; University of North Carolina; Chapel Hill North Carolina USA
4. Lineberger Comprehensive Cancer Center; University of North Carolina; Chapel Hill North Carolina USA
5. Center for Gastrointestinal Biology and Disease, University of North Carolina; Chapel Hill North Carolina USA
6. Department of Thoracic and Cardiovascular Surgery; University of Texas M.D. Anderson Cancer Center; Houston Texas USA