1. Department of Otorhinolaryngology, Östersund Hospital, Östersund, Sweden
2. Department of Otorhinolaryngology, Karolinska University Hospital, Stockholm, Sweden
3. Department of Surgical Sciences, Otorhinolaryngology, Uppsala University Hospital, Uppsala, Sweden
4. Department of Clinical Sciences, Otorhinolaryngology, Umeå University, site Sundsvall, Umeå, Sweden
5. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
6. Division of CLINTEC, Department of Otorhinolaryngology, Karolinska Institutet, Stockholm, Sweden