[1] Univ Teesside, Ctr Hlth & Med Res, Middlesbrough TS1 3BA, Cleveland, England
[2] Univ Newcastle Upon Tyne, Dept Epidemiol & Publ Hlth, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[3] Univ Newcastle Upon Tyne, Dept Primary Care, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[4] Univ Newcastle Upon Tyne, Ctr Urban & Reg Dev Studies, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England