[1] Te Omanga Hosp, Lowe Hutt, New Zealand
[2] Univ Otago, Dept Prevent & Social Med, Dunedin, New Zealand
[3] Univ Auckland, Dept Gen Practice & Primary Care, Auckland, New Zealand
[4] Univ Otago, Biostat Grp, Wellington, New Zealand
[5] Tu Kotahi Maori Asthma & Res Trust, 7-9 Barnes St, Lower Hutt 5010, New Zealand
[6] Univ Otago, Dunedin Sch Med, Social & Behav Res Unit, Te Hunga Rangahau Whanonga Papori, Dunedin, New Zealand
[7] Univ Otago, Dunedin Sch Med, Dept Prevent & Social Med, Te Tari Hauora Tumatanui, Dunedin, New Zealand
[8] Univ Otago, Dunedin Sch Med, Dept Prevent & Social Med, 362 Leith St North,POB 56, Dunedin 9054, New Zealand