[1] UNSW Sydney, Kirby Inst, Sydney, NSW, Australia
[2] British Columbia Ctr Dis Control, Vancouver, BC, Canada
[3] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC, Canada
[4] Oslo Univ Hosp, Dept Gastroenterol, Oslo, Norway
[5] Akershus Univ Hosp, Oslo, Norway
[6] Univ Dundee, Ninewells Hosp & Med Sch, Dundee, Scotland
[7] Univ Bristol, Populat Hlth Sci, Bristol, Avon, England
[8] Ctr Hosp Univ Montreal, Montreal, PQ, Canada