[1] Univ Adelaide, Sch Med, Adelaide, SA, Australia
[2] Royal Coll Surgeons Ireland, Div Populat Hlth Sci PHS, Emergency Care Res Unit, Dublin 2, Ireland
[3] Flinders Univ S Australia, Coll Med & Publ Hlth, Adelaide, SA, Australia
[4] Queen Elizabeth Hosp, Cent Adelaide Local Hlth Network, Resp Med Unit, Adelaide, SA, Australia
[5] Royal Coll Surgeons Ireland, Mercer Lib, Dublin, Ireland
[6] Univ Queensland, Sch Publ Hlth, Habit Res Grp, Brisbane, Qld, Australia
[7] Our Ladys Childrens Hosp Crumlin, Natl Childrens Res Ctr, Dublin, Ireland
[8] Cork Univ Hosp, Cork, Ireland