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Early Exposure to Dogs and Farm Animals and the Risk of Childhood Asthma
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular epidemiology.ORCID iD: 0000-0003-2071-5866
Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden..
Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden..
Orebro Univ Hosp, Clin Epidemiol & Biostat, Orebro, Sweden.;Univ Orebro, Sch Hlth & Med Sci, SE-70182 Orebro, Sweden..ORCID iD: 0000-0002-3649-2639
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2015 (English)In: JAMA pediatrics, ISSN 2168-6203, E-ISSN 2168-6211, Vol. 169, no 11, e153219Article in journal (Refereed) PublishedText
Abstract [en]

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.

Place, publisher, year, edition, pages
2015. Vol. 169, no 11, e153219
National Category
Respiratory Medicine and Allergy
URN: urn:nbn:se:uu:diva-268804DOI: 10.1001/jamapediatrics.2015.3219ISI: 000364430000002OAI: oai:DiVA.org:uu-268804DiVA: diva2:881099
Swedish Research Council, 2011-3060Swedish Research Council, 80748301Swedish Research Council, 340-2013-5867Stockholm County Council, 520344Stockholm County Council, 530422Stockholm County Council, 541322Swedish Heart Lung Foundation, 20100633Swedish Heart Lung Foundation, 20120480
Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2016-01-26Bibliographically approved

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Fall, ToveFall, KatjaIngelsson, Erik
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