1. Department of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, The OLIN unit, Umeå University, Umeå, Sweden
2. Department of Health Sciences, Division of Nursing, Luleå University of Technology, Luleå, Sweden
3. Department of Respiratory Medicine and Allergology, Institution for Clinical Sciences, Lund University, Lund, Sweden
4. Department of Public Health and Clinical Medicine, Division of Medicine, Umeå University, Umeå, Sweden