Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Feb;50(2):222-230.
doi: 10.1111/cea.13542. Epub 2019 Dec 28.

Season of birth, childhood asthma and allergy in a nationwide cohort-Mediation through lower respiratory infections

Catarina Almqvist  1   2 , Sara Ekberg  1 , Samuel Rhedin  1 , Fang Fang  1 , Tove Fall  3 , Cecilia Lundholm  1
Affiliations

Season of birth, childhood asthma and allergy in a nationwide cohort-Mediation through lower respiratory infections

Catarina Almqvist et al. Clin Exp Allergy. 2020 Feb.

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.

Keywords: allergy; asthma; epidemiology; pollen; register; respiratory infectious disease; season.

PubMed Disclaimer

References

REFERENCES

    1. Kihlstrom A., Lilja G., Pershagen G., Hedlin G.. Exposure to high doses of birch pollen during pregnancy, and risk of sensitization and atopic disease in the child. Allergy. 2003;58(9):871-877.
    1. Lowe A.J., Olsson D., Braback L., Forsberg B.. Pollen exposure in pregnancy and infancy and risk of asthma hospitalisation - a register based cohort study. Allergy Asthma Clin Immunol. 2012;8(1):17.
    1. Kihlstrom A., Lilja G., Pershagen G., Hedlin G.. Exposure to birch pollen in infancy and development of atopic disease in childhood. J Allergy Clin Immunol. 2002;110(1):78-84.
    1. Bjorksten F., Suoniemi I.. Time and intensity of first pollen contacts and risk of subsequent pollen allergies. Acta Med Scand. 1981;209(4):299-303.
    1. Quoix E., Bessot J.C., Kopferschmitt-Kubler M.C., Fraisse P., Pauli G.. Positive skin tests to aero-allergens and month of birth. Allergy. 1988;43(2):127-131.

Publication types