1. Department of Internal Medicine, Krefting Research Centre, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
2. Obstructive Lung Disease In Northern Sweden (OLIN) studies, Department of Medicine, Sunderby Central Hospital of Norrbotten, Luleå, Sweden.
3. Department of Public Health and Clinical Medicine/Environmental Medicine and Occupation, University of Umeå, Umeå, Sweden.
4. Department of Paediatrics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
5. Department of Environmental and Occupational Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden