[1] Univ Dusseldorf, Ctr Hlth & Soc, Fac Med, Inst Occupat & Social Med, Univ Str 1, D-40225 Dusseldorf, Germany
[2] Heidelberg Univ, Mannheim Inst Publ Hlth Social & Prevent Med, Mannheim Med Fac, Mannheim, Germany
[3] Univ Dusseldorf, Social Sci Inst, Fac Philosophy, D-40225 Dusseldorf, Germany
[4] Univ Regensburg, Dept Epidemiol & Prevent Med, Div Med Sociol, D-93053 Regensburg, Germany
[5] Univ Brighton, Brighton & Sussex Med Sch, Div Publ Hlth & Primary Care, Falmer, England
[6] Univ Edinburgh, Sch Med, Asthma UK Ctr Appl Res, Allergy & Resp Res Grp,Ctr Med Informat, Edinburgh, Midlothian, Scotland
[7] Brigham & Womens Hosp, Div Gen Internal Med & Primary Care, 75 Francis St, Boston, MA 02115 USA
[8] Harvard Univ, Sch Med, Dept Med, Boston, MA USA