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 
1
Department of Respiratory Medicine and Allergology, University Hospital, Umeå, Sweden
2
National Respiratory Center, Department of Anesthesia and Intensive Care, Karolinska Institute, Danderyd Hospital, Stockholm, Sweden
3
Department of Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden
4
Department of Pulmonary Medicine, Landspitali University Hospital, Reykjavik, Iceland
5
Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway
6
Institute of Medicine, University of Bergen, Norway
7
Department of Public Health and Clinical Medicine, Division of Epidemiology and Public Health Sciences, Umeå University, Sweden
8
Center for Clinical Research, Haukeland University Hospital, Bergen, Norway
9
Department of Occupational and Environmental Medicine and Allergology, Sahlgrenska University Hospital, Göteborg, Sweden