[1] Univ Coll Copenhagen, Dept Midwifery Physiotherapy & Occupat Therapy & P, Copenhagen, Denmark
[2] Hvidovre Univ Hosp, Dept Resp Med, Resp Res Unit, Hvidovre, Denmark
[3] Univ Copenhagen, Dept Publ Hlth, Sect Social Med, Copenhagen, Denmark
[4] Univ Southern Denmark, Natl Inst Publ Hlth, Copenhagen, Denmark
[5] Nordsjaellands Hosp, Dept Clin Res, Copenhagen, Denmark
[6] Univ Copenhagen, Dept Clin Med, Copenhagen, Denmark