International Rhinologic Society Rhinology 0300-0729 2025 11 30 The prevalence of primary chronic rhinosinusitis in young adults from a Swedish birth cohort EN K. ÅbergDepartment of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stockholm, 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 S.K. Georén Department of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stockholm, Sweden L.O. CardellDepartment of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institutet, Stockholm, Sweden Department of Ear, Nose and Throat Diseases, Karolinska University Hospital, Stockholm, Sweden I. Kull Department of Clinical Science and Education Södersjukhuset, Karolinska Institutet 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 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, Stockholm, Sweden M. van HageDepartment of Medicine Solna, Division of Immunology and Respiratory Medicine, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden Center for Molecular Medicine, Karolinska University Hospital Stockholm, Sweden M. Westman Department of Medicine Solna, Division of Immunology and Respiratory Medicine, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden Journal Article 3270 10.4193/Rhin24.048 BACKGROUND: Chronic rhinosinusitis (CRS) is common worldwide but scarcely studied among young adults. The aim was to investigate prevalence, clinical features, comorbidity, and mucosal inflammatory patterns of CRS among 24-year-olds in a populationbased study.METHOD: 3037 subjects from the birth cohort BAMSE (Barn/children Allergy Milieu Stockholm Epidemiology) had complete questionnaire answers on CRS at the 24-year-follow-up. Subjects fulfilling the European Position Paper on Rhinosinusitis (EPOS) criteria of CRS at 16 and/or 24 years (n=141), were invited to a clinical examination. We examined 81 subjects. Sixty-eight subjects were included, of whom 40 had CRSsNP, 2 CRSwNP and 26 CRS symptoms only. Twenty-three controls without CRS from BAMSE were included. Nasal endoscopy was performed, IgE against airborne allergens and cytokine gene expression in nasal lavage (NAL) were analyzed. RESULTS: The questionnaire-based CRS prevalence was 4.1%, of which 2.2% was endoscopically verified. Sensitization to airborne allergens was more often seen among CRSsNP and “CRS symptoms only”, compared to controls. Among CRS subjects overall, the proportion of asthma, AR, atopic eczema, and sensitization to airborne allergens was significantly higher compared to the rest of the cohort. The gene expression of IL-1b and IL-8 in NAL was elevated among CRSsNP and “CRS symptoms only” compared to controls, with a trend for TNF-a and MPO. CONCLUSIONS: The prevalence of primary CRS was estimated to 2-4%. There was a significant association between CRS and atopic diseases in this age group. The NAL profile showed signs of type-1 inflammation.