[1] UCL, UCL Resp Med, London, England
[2] Hosp Univ Virgen del Rocio, Inst Biomed Sevilla IBiS, Seville, Spain
[3] Inst Salud Carlos III, Ctr Invest Red Enfermedades Resp CIBERES, Madrid, Spain
[4] Ludwig Boltzmann Inst COPD & Resp Epidemiol, Vienna, Austria
[5] Hosp 12 Octubre, Inst Invest i 12, E-28041 Madrid, Spain
[6] Queen Mary Univ London, Barts & London Sch Med & Dent, London, England