1. Department of Respiratory Medicine, School of Medical Sciences, Örebro University , Örebro, Sweden
2. School of Medical Sciences, Örebro University , Örebro, Sweden
3. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University , Örebro, Sweden
4. Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet , Stockholm, Sweden
5. Department of Epidemiology and Public Health, University College , London, UK
6. Department of Public Health and Caring Sciences, Family Medicine and Preventive Medicine, Uppsala University , Uppsala, Sweden
7. Department of Medical Sciences: Respiratory; Allergy and Sleep Research, Uppsala University , Uppsala, Sweden