[1] Harvard Univ, TH Chan Sch Publ Hlth, Boston, MA 02115 USA
[2] Harvard Med Sch, Div Gastroenterol, Boston, MA USA
[3] Harvard Med Sch, Massachusetts Gen Hosp, Dept Med, Clin & Translat Epidemiol Unit, Boston, MA USA
[4] Karolinska Inst, Clin Epidemiol Unit, Solna, Sweden