National Heart and Lung Institute, Imperial College London, London, UK. Centre de Recherche cardio-thoracique de Bordeaux, Univ-Bordeaux, Pessac, France. Service des Maladies Respiratoires, CHU Bordeaux, Pessac, France. Department of Medicine and Rehabilitation, Levanger Hospital, Nord-Trøndelag Hospital Trust, Levanger, Norway. HUNT Research Centre, Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Levanger, Norway. Respiratory Group, The George Institute for Global Health, Sydney, NSW, Australia. COPD Center, Department of Respiratory Medicine and Allergology, Sahlgrenska University Hospital, Gothenburg, Sweden. Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.