Karl A Franklin1,2
, Christer Janson3
, Thórarinn Gíslason4
, Amund Gulsvik5,6
, Maria Gunnbjörnsdottir3
, Birger N Laerum5,6
, Eva Lindberg3
, Eva Norrman1
, Lennarth Nyström7
, Ernst Omenaas6,8
, Kjell Torén9
and Cecilie Svanes5,6 
1Department of Respiratory Medicine and Allergology, University Hospital, Umeå, Sweden
2National Respiratory Center, Department of Anesthesia and Intensive Care, Karolinska Institute, Danderyd Hospital, Stockholm, Sweden
3Department of Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden
4Department of Pulmonary Medicine, Landspitali University Hospital, Reykjavik, Iceland
5Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway
6Institute of Medicine, University of Bergen, Norway
7Department of Public Health and Clinical Medicine, Division of Epidemiology and Public Health Sciences, Umeå University, Sweden
8Center for Clinical Research, Haukeland University Hospital, Bergen, Norway
9Department of Occupational and Environmental Medicine and Allergology, Sahlgrenska University Hospital, Göteborg, Sweden