International Rhinologic Society Rhinology 0300-0729 2026 04 16 Chronic rhinosinusitis in a birth cohort: symptom trajectories and early-life risk factors up to young adulthood EN K. ÅbergDepartment of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stock-holm, Sweden Medical unit Head Neck Lung and Skin cancer, Department of Head and Neck Surgery, Karolinska University Hospital, Stockholm, Sweden A. AsarnojDepartment of Women’s and Children's Health, Karolinska Institutet, Stockholm, Sweden Astrid Lindgren’s Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden A. AsarnojDepartment of Women’s and Children's Health, Karolinska Institutet, Stockholm, Sweden Astrid Lindgren’s Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden L.O. CardellDepartment of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stock-holm, Sweden Department of Ear, Nose and Throat Diseases, Karolinska University Hospital, Stockholm, Sweden I. KullDepartment of Clinical Science and Education Södersjukhuset, Karolinska Institutet, Stockholm, Sweden Sachs’ Children and Youth Hospital, Södersjukhuset, Stockholm, Sweden A. BergströmDepartment of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden Center for Occupational and Environmental Medicine, Region Stockholm, Sweden E. MelénDepartment of Clinical Science and Education Södersjukhuset, Karolinska Institutet, Stockholm, Sweden Sachs’ Children and Youth Hospital, Södersjukhuset, Stockholm, Sweden M. Holmström Department of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stock-holm, Sweden M. van HageDepartment of Medicine Solna, Division of Immunology and Respiratory Medicine, Karolinska Institutet, Stockholm, Sweden Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden Center for Molecular Medicine, Karolinska University Hospital Stockholm, Sweden M. Westman Department of Medicine Huddinge, Clinical Lung and Allergy Research Unit, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden Journal Article 3452 10.4193/Rhin26.079 BACKGROUND: Chronic rhinosinusitis (CRS) is common worldwide in adults, but development of CRS has rarely been studied longitudinally in birth-cohorts. The aim was to investigate development of upper airway symptoms from childhood to young adulthood and to identify early risk factors for CRS at 24 years, in a population-based birth cohort. METHOD: 3037 subjects from the BAMSE (Barn/children Allergy Milieu Stockholm Epidemiology) cohort had complete question-naire answers on CRS at the 24-year-follow-up. Subjects fulfilling European Position Paper on Rhinosinusitis (EPOS) criteria of CRS at 16 and/or 24 years (n=141) were invited to a clinical examination with nasal endoscopy and interviews. Among these, 68 had clinically verified CRS symptoms. Symptoms and clinical status were compared with questionnaire-based answers on symptoms and potential risk factors for CRS, in early childhood. RESULTS: Among subjects with CRS symptoms at 24 years, > 60% reported upper airway symptoms already at 16 years. In the same group, a significant association was observed with a history of otitis media < 1 year and with heredity for atopic diseases. Moreover, the proportion of atopic features such as asthma, allergic rhinitis and eczema were significantly higher at 4, 8 and 16 years in this group. No clear association was found between CRS at 24 years and early RS infection, antibiotic use