[1] Univ Calif San Diego, Joint Doctoral Program Publ Hlth, San Diego, CA 92103 USA
[2] San Diego State Univ, La Jolla, CA USA
[3] Johns Hopkins Bloomberg Sch Publ Hlth, Baltimore, MD USA
[4] John Cochran VA Med Ctr, St Louis, MO USA
[5] St Louis Univ, Sch Med, Div Gastroenterol, St Louis, MO USA
[6] Benaroya Res Inst Virginia Mason, Seattle, WA USA
[7] Univ Calif San Diego, Div Pediat Gastroenterol & Nutr, La Jolla, CA 92093 USA