Catarina Almqvist1,2, Sara Ekberg1, Samuel Rhedin1, Fang Fang1, Tove Fall3, Cecilia Lundholm1. 1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. 2. Pediatric Allergy and Pulmonology Unit, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden. 3. Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Abstract
BACKGROUND: Previous studies have suggested an association between season of birth and risk of childhood asthma and allergic disease. The association may be modified by birth year and region, or mediated by respiratory tract infections. OBJECTIVE: We aimed to estimate the association between season of birth and risk of childhood asthma/wheeze or allergic rhinoconjunctivitis in a population-based setting, and the mediating effect of lower respiratory infections. METHODS: Two population-based cohorts were identified from the nationwide Swedish Medical Birth, Patient and Prescribed Drug Registers. The association between birth month/season and asthma/wheeze incidence was analysed using Cox proportional regression in the younger cohort born 2005-2010 (n = 582 494) and asthma/allergic rhinoconjunctivitis prevalence during the 7th year of life using log-binomial models in the older cohort born 2001-2004 (n = 367 583). Interactions were formally tested. Mediation analyses to address the effect of lower respiratory infections were performed in the older cohort using the R package "medflex." RESULTS: Children born during fall and winter had an increased risk of asthma/wheeze after 2 years of age in the younger cohort: hazard ratio 1.24 (95% confidence interval, CI 1.17, 1.33) for winter and risk of prevalent asthma during their 7th year of life in the older cohort; prevalence ratio (PR) 1.12 (95% CI 1.08, 1.16) for winter. These estimates were partly mediated by lower respiratory infections; the indirect effect for winter compared with summer was PR 1.03 (95% CI 1.03, 1.04). The association was similar for allergic rhinoconjunctivitis in the 7th year of life, but not mediated by respiratory infections. CONCLUSION: We found that the association between season of birth and risk of childhood asthma/wheeze, but not allergic rhinoconjunctivitis, is partly mediated through lower respiratory infections. CLINICAL RELEVANCE: This has important implications for patient care, such as asthma management programmes to notify timing of seasonality for viral respiratory tract infections.
BACKGROUND: Previous studies have suggested an association between season of birth and risk of childhood asthma and allergic disease. The association may be modified by birth year and region, or mediated by respiratory tract infections. OBJECTIVE: We aimed to estimate the association between season of birth and risk of childhood asthma/wheeze or allergic rhinoconjunctivitis in a population-based setting, and the mediating effect of lower respiratory infections. METHODS: Two population-based cohorts were identified from the nationwide Swedish Medical Birth, Patient and Prescribed Drug Registers. The association between birth month/season and asthma/wheeze incidence was analysed using Cox proportional regression in the younger cohort born 2005-2010 (n = 582 494) and asthma/allergic rhinoconjunctivitis prevalence during the 7th year of life using log-binomial models in the older cohort born 2001-2004 (n = 367 583). Interactions were formally tested. Mediation analyses to address the effect of lower respiratory infections were performed in the older cohort using the R package "medflex." RESULTS:Children born during fall and winter had an increased risk of asthma/wheeze after 2 years of age in the younger cohort: hazard ratio 1.24 (95% confidence interval, CI 1.17, 1.33) for winter and risk of prevalent asthma during their 7th year of life in the older cohort; prevalence ratio (PR) 1.12 (95% CI 1.08, 1.16) for winter. These estimates were partly mediated by lower respiratory infections; the indirect effect for winter compared with summer was PR 1.03 (95% CI 1.03, 1.04). The association was similar for allergic rhinoconjunctivitis in the 7th year of life, but not mediated by respiratory infections. CONCLUSION: We found that the association between season of birth and risk of childhood asthma/wheeze, but not allergic rhinoconjunctivitis, is partly mediated through lower respiratory infections. CLINICAL RELEVANCE: This has important implications for patient care, such as asthma management programmes to notify timing of seasonality for viral respiratory tract infections.
Authors: Victoria Coathup; Elaine Boyle; Claire Carson; Samantha Johnson; Jennifer J Kurinzcuk; Alison Macfarlane; Stavros Petrou; Oliver Rivero-Arias; Maria A Quigley Journal: BMJ Date: 2020-11-25
Authors: Rosa Bellmann-Weiler; Miriam Ladstätter; Falko Schüllner; Manfred Nairz; Martina Zimmermann; Anna-Maria Koller; Silvia Blunder; Helene Naschberger; Werner Klotz; Manfred Herold; Sylvia Kerndler; Martina Jeske; David Haschka; Verena Petzer; Andrea Schroll; Thomas Sonnweber; Ivan Tancevski; Gernot Fritsche; Mariana E G de Araujo; Taras Stasyk; Lukas A Huber; Andrea Griesmacher; Igor Theurl; Günter Weiss Journal: Sci Rep Date: 2021-01-26 Impact factor: 4.379