Early exposure to dogs and farm animals and the risk of childhood asthma
Author: Fall, Tove; Lundholm, Cecilia; Örtqvist, Anne K; Fall, Katja; Fang, Fang; Hedhammar, Åke; Kämpe, Olle; Ingelsson, Erik; Almqvist, Catarina
Department: Inst för medicinsk epidemiologi och biostatistik / Dept of Medical Epidemiology and Biostatistics
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Abstract
IMPORTANCE: The association between early exposure to animals and childhood asthma is not clear, and previous studies have yielded contradictory results.
OBJECTIVE: To determine whether exposure to dogs and farm animals confers a risk of asthma.
DESIGN, SETTING AND PARTICIPANTS: In a nationwide cohort study, the association between early exposure to dogs and farm animals and the risk of asthma was evaluated and included all children born in Sweden from January 1, 2001, to December 31, 2010 (N = 1,011,051), using registry data on dog and farm registration, asthma medication, diagnosis, and confounders for parents and their children. The association was assessed as the odds ratio (OR) for a current diagnosis of asthma at age 6 years for school-aged children and as the hazard ratio (HR) for incident asthma at ages 1 to 5 years for preschool-aged children. Data were analyzed from January 1, 2007, to September 30, 2012.
EXPOSURES: Living with a dog or farm animal.
MAIN OUTCOMES AND MEASURES: Childhood asthma diagnosis and medication used.
RESULTS: Of the 1,011,051 children born during the study period, 376,638 preschool-aged (53,460 [14.2%] exposed to dogs and 1729 [0.5%] exposed to farm animals) and 276,298 school-aged children (22,629 [8.2%] exposed to dogs and 958 [0.3%] exposed to farm animals) were included in the analyses. Of these, 18,799 children (5.0%) in the preschool-aged children's cohort experienced an asthmatic event before baseline, and 28,511 cases of asthma and 906,071 years at risk were recorded during follow-up (incidence rate, 3.1 cases per 1000 years at risk). In the school-aged children's cohort, 11,585 children (4.2%) experienced an asthmatic event during the seventh year of life. Dog exposure during the first year of life was associated with a decreased risk of asthma in school-aged children (OR, 0.87; 95% CI, 0.81-0.93) and in preschool-aged children 3 years or older (HR, 0.90; 95% CI, 0.83-0.99) but not in children younger than 3 years (HR, 1.03; 95% CI, 1.00-1.07). Results were comparable when analyzing only first-born children. Farm animal exposure was associated with a reduced risk of asthma in both school-aged children and preschool-aged children (OR, 0.48; 95% CI, 0.31-0.76, and HR, 0.69; 95% CI, 0.56-0.84), respectively.
CONCLUSIONS AND RELEVANCE: In this study, the data support the hypothesis that exposure to dogs and farm animals during the first year of life reduces the risk of asthma in children at age 6 years. This information might be helpful in decision making for families and physicians on the appropriateness and timing of early animal exposure.
OBJECTIVE: To determine whether exposure to dogs and farm animals confers a risk of asthma.
DESIGN, SETTING AND PARTICIPANTS: In a nationwide cohort study, the association between early exposure to dogs and farm animals and the risk of asthma was evaluated and included all children born in Sweden from January 1, 2001, to December 31, 2010 (N = 1,011,051), using registry data on dog and farm registration, asthma medication, diagnosis, and confounders for parents and their children. The association was assessed as the odds ratio (OR) for a current diagnosis of asthma at age 6 years for school-aged children and as the hazard ratio (HR) for incident asthma at ages 1 to 5 years for preschool-aged children. Data were analyzed from January 1, 2007, to September 30, 2012.
EXPOSURES: Living with a dog or farm animal.
MAIN OUTCOMES AND MEASURES: Childhood asthma diagnosis and medication used.
RESULTS: Of the 1,011,051 children born during the study period, 376,638 preschool-aged (53,460 [14.2%] exposed to dogs and 1729 [0.5%] exposed to farm animals) and 276,298 school-aged children (22,629 [8.2%] exposed to dogs and 958 [0.3%] exposed to farm animals) were included in the analyses. Of these, 18,799 children (5.0%) in the preschool-aged children's cohort experienced an asthmatic event before baseline, and 28,511 cases of asthma and 906,071 years at risk were recorded during follow-up (incidence rate, 3.1 cases per 1000 years at risk). In the school-aged children's cohort, 11,585 children (4.2%) experienced an asthmatic event during the seventh year of life. Dog exposure during the first year of life was associated with a decreased risk of asthma in school-aged children (OR, 0.87; 95% CI, 0.81-0.93) and in preschool-aged children 3 years or older (HR, 0.90; 95% CI, 0.83-0.99) but not in children younger than 3 years (HR, 1.03; 95% CI, 1.00-1.07). Results were comparable when analyzing only first-born children. Farm animal exposure was associated with a reduced risk of asthma in both school-aged children and preschool-aged children (OR, 0.48; 95% CI, 0.31-0.76, and HR, 0.69; 95% CI, 0.56-0.84), respectively.
CONCLUSIONS AND RELEVANCE: In this study, the data support the hypothesis that exposure to dogs and farm animals during the first year of life reduces the risk of asthma in children at age 6 years. This information might be helpful in decision making for families and physicians on the appropriateness and timing of early animal exposure.
Institution:
- Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
- Clinical Epidemiology and Biostatistics, Örebro University Hospital, Örebro, Sweden
- School of Health and Medical Sciences, Örebro University, Örebro, Sweden
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
- Centre for Molecular Medicine, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden
- Astrid Lindgren Children's Hospital, Lung and Allergy Unit, Karolinska University Hospital, Stockholm, Sweden
Citation: JAMA Pediatr. 2015 Nov;169(11):e153219.
Citation DOI: 10.1001/jamapediatrics.2015.3219
Citation PMID: 26523822
Citation ISI: 000364430000002
Publishing journal: JAMA Pediatrics
Eprint status: Peer Reviewed
Version: Published
Issue date: 2017-01-16
Sponsorship:
- Swedish Research Council, 2011-3060
- Swedish Research Council, SIMSAM 80748301, 340-2013-5867
- Stockholm County Council (ALF), 520344, 530422, 541322
- Strategic Research Program in Epidemiology at Karolinska Institutet
- Swedish Heart Lung Foundation, 20100633, 20120480
- Bror Hjerpstedts stiftelse
- Tore Nilssons stiftelse
- Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas)
- Torsten & Ragnar Söderberg Foundation
- NovoNordisk Foundation
Rights:
Article is made available in accordance with the publisher's policy and may be subject to copyright law. Please refer to the publisher's site for terms of use.
Publication year: 2015
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