Self-reported helminth infection is associated with increased respiratory symptoms in the RHINE IV study.

<bold>Background:</bold> Helminths can lead to a polarized systemic Th2-repsonse that can be long-lasting. Data addressing helminth infections and their association with allergies and asthma is lacking in Europe, where high sanitary standards are believed to have broken the life cycle for many helminthiases. However, we have shown that seropositivity towards helminths in Europe can be as high as 30% and associated with lower lung function and asthma symptoms. <bold>Aim:</bold> investigate the association between self-reported helminth infections and respiratory and allergic symptoms in a cross-sectional study. <bold>Methods:</bold> 9694 participants (53% women, mean age 62 years) answered questions on helminth infections and respiratory and allergic symptoms in the Respiratory Health in Northern Europe (RHINE) IV study (2020-22) from Bergen (Norway, 16.4%), Reykjavik (Iceland, 10.9%), Tartu (Estonia, 10.4%), Gothenburg (13.8%), Umea (16%), Uppsala (Sweden, 17.9%), and Aarhus (Denmark, 14.7%). Associations between helminth infections and the outcomes were studied by multivariate logistic regression models adjusted for age, sex, smoking, number of children and marital status. <bold>Results:</bold> 8.7% reported having ever had a helminth infection, ranging from 3.6% (in Aarhus) to 21.1% (in Tartu). Self-reported helminth infection was associated with increased odds of reporting allergic rhinitis (aOR 1.15; 95% CI 1.03-1.28), skin allergy (aOR 1.35; 1.07-1.71), and a higher score for respiratory symptoms (1 vs 0: aOR 1.36; 1.22-1-53; 2 vs 0: 1.48 1.14-1.91; >2 vs 0; 1.92; 1.64-2.25). <bold>Conclusion:</bold> Helminth infections might be underreported in Europe and an overlooked risk factor for respiratory and allergic symptoms.