1. Unit for Lung and Airway Research, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
2. Division of Respiratory Medicine and Allergology, Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
3. Department of Respiratory Medicine and Allergology, Sahlgrenska University Hospital, Gothenburg, Sweden
4. Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
5. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan; and
6. Karolinska Severe COPD Center, Department of Respiratory Medicine and Allergy, Karolinska University Hospital, Stockholm, Sweden