1. Affiliations of authors: Division of Epidemiology, Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX (CCM); Department of Medicine (HKS, JAB, RSS), Department of Surgery (KBS), Center for Gastrointestinal Biology and Disease (JAB, RSS), Department of Epidemiology (JAB, RSS, JLL), and Department of Sociology (YCY), University of North Carolina at Chapel H