[1] Univ Newcastle, Hunter Med Res Inst, Fac Hlth & Med, Sch Med & Publ Hlth, Callaghan, NSW 2308, Australia
[2] Univ Newcastle, Prior Res Ctr Hlth Behav, Callaghan, NSW 2308, Australia
[3] Univ Newcastle, Hlth Behav Res Grp, Callaghan, NSW 2308, Australia
[4] Hunter Med Res Inst, New Lambton, NSW, Australia
[5] Australian Natl Univ, Natl Ctr Epidemiol & Populat Hlth, Canberra, ACT 0200, Australia
[6] UCL, Dept Epidemiol & Publ Hlth, Hlth Behav Res Ctr, London WC1E 6BT, England
[7] Univ Nebraska, Med Ctr, Coll Publ Hlth, Dept Hlth Promot Social & Behav Hlth, Omaha, NE USA
[8] Hunter Med Res Inst, Newcastle, NSW, Australia