1. Center for Gastrointestinal Biology and Disease, University of North Carolina School of Medicine, and School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (C.E.G.)
2. University of North Carolina School of Pharmacy and Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (A.C.K.)
3. School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (J.K.E., J.L.L., S.P.H., V.P.)
4. School of Public Health and the Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (T.S.)
5. Center for Gastrointestinal Biology and Disease, University of North Carolina School of Medicine, Chapel Hill, North Carolina (L.A.B., R.S.S., A.F.P.).