[1] Turku Univ Hosp, Div Med, Dept Pulm Dis, Turku, Finland
[2] Univ Turku, Dept Pulm Dis & Clin Allergol, Lantinen Rantakatu 37, FI-20100 Turku, Finland
[3] Helsinki Univ Hosp, Heart & Lung Ctr, Helsinki, Finland
[4] Univ Helsinki, Dept Med, Helsinki, Finland
[5] Univ Oulu, Res Unit Internal Med, Resp Med, Oulu, Finland
[6] Oulu Univ Hosp, Med Res Ctr Oulu, Oulu, Finland
[7] Seinajoki Cent Hosp, Dept Resp Med, Seinajoki, Finland
[8] Univ Tampere, Fac Med & Hlth Technol, Tampere, Finland
[9] Univ Helsinki, Fac Med, Individrug Res Program, Res Programs Unit, Helsinki, Finland
[10] Univ Turku, Dept Biostat, Turku, Finland