[1] Albert Einstein Coll Med, Dept Epidemiol & Populat Hlth, Belfer Bldg,Room 1308,1300 Morris Pk Ave, Bronx, NY 10461 USA
[2] Inst Salud Carlos III, Natl Ctr Epidemiol, Madrid, Spain
[3] San Diego State Univ, Grad Sch Publ Hlth, Inst Behav & Community Hlth, San Diego, CA 92182 USA
[4] Univ Minnesota, Dept Lab Med & Pathol, Minneapolis, MN 55455 USA
[5] Univ Illinois, Sch Publ Hlth, Div Epidemiol & Biostat, Chicago, IL USA
[6] Univ Miami, Miller Sch Med, Dept Med, Div Gastroenterol, Miami, FL 33136 USA