1. Clinical Epidemiology Division, Department of Medicine Solna, Karolinska Institutet , Stockholm , Sweden
2. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Faculty of Medicine and Health, Örebro University , Örebro , Sweden
3. Department of Occupational and Environmental Dermatology, Skåne University Hospital, Lund University , Lund , Sweden
4. Department of Epidemiology and Public Health, University College London , UK