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Early exposure to dogs and farm animals and the risk of childhood asthma

By Tove Fall, Cecilia Lundholm, Anne K. Ortqvist, Katja Fall, Fang Fang, Ake Hedhammar, Olle Kampe, Erik Ingelsson, Catarina Almqvist

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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.


Katie Carroll

Date 2017
Publication Title JAMA Pediatrics
Volume 169
Issue 11
Publisher Karolinska Institutet
DOI 10.1001/jamapediatrics.2015.3219
Language English
Additional Language English
Cite this work

Researchers should cite this work as follows:

  1. Animal roles
  2. Asthma
  3. breath
  4. Dogs
  5. Exposure
  6. Farm animals
  7. Food animals
  8. Health
  9. Livestock
  10. Mammals
  11. Pet exposure
  12. Pet ownership
  13. Pets and companion animals