1. Department of Otorhinolaryngology and Head and Neck Surgery, Oulu University Hospital, Oulu, Finland
2. PEDEGO Research Unit, University of Oulu, Oulu, Finland
3. Medical Research Center Oulu, Oulu, Finland
4. Division of Operative Care and Oulu University Hospital and Research Unit of Surgery, Anesthesia and Intensive care, University of Oulu, Oulu, Finland
5. Audiological Research Center, Faculty of Medicine and Health, Örebro University, Örebro, Sweden