[1] Orebro Univ, Sch Med Sci, Orebro, Sweden
[2] Orebro Univ, Clin Epidemiol & Biostat, Orebro, Sweden
[3] Karolinska Inst, Dept Med, Clin Epidemiol Unit, Stockholm, Sweden
[4] UCL, Dept Epidemiol & Publ Hlth, London, England
[5] Uppsala Univ, Dept Publ Hlth & Caring Sci, Family Med & Prevent Med, Uppsala, Sweden
[6] Uppsala Univ, Dept Med Sci Resp Allergy & Sleep Res, Uppsala, Sweden
[7] Orebro Univ, Sch Med Sci, Dept Resp Med, Orebro, Sweden