1. Centre for Clinical Research, Uppsala University, Västmanland County Hospital, Västerås, Sweden
2. Department of Medical Sciences, Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden
3. Department of Public Health and Caring Sciences, Family Medicine and Preventive Medicine, Uppsala University, Uppsala, Sweden
4. Department of Respiratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
5. Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden
6. NVS, Section for Family Medicine and Primary Care, Karolinska Institutet, Stockholm, Sweden
7. Academic Primary Care Centre, Region Stockholm, Sweden
8. Department of Medicine, Clinical Epidemiology Division, Karolinska Institute, Stockholm, Sweden
9. Centre for Clinical Research and Education, Karlstad, Sweden
10. Faculty of Medicine and Health, School of Medical Sciences, Örebro University, Örebro, Sweden
11. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
12. Department of Epidemiology and Public Health, University College London, London, UK