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Early exposure to dogs, farm animals associated with lower asthma risk

The JAMA Network Journals

A reduced risk for childhood asthma at the age of six was associated with exposure to dogs or farm animals during a child's first year of life, according to an article published online by JAMA Pediatrics.

Childhood asthma is a global health concern. A number of environmental factors have been associated with either increased or decreased risk of asthma.

Tove Fall, Ph.D., of Uppsala University, Sweden, and coauthors looked at the association between animal exposure and asthma in a nationwide study that included all of the more than 1 million children born in Sweden from 2001 through 2010. Registry data was used for information on dog and farm animals, as well as asthma medication and diagnosis.

The analyses included 376,638 preschool-age (53,460 exposed to dogs and 1,729 exposed to farm animals) and 276,298 school-age children (22,629 exposed to dogs and 958 exposed to farm animals). Of those children, 18,799 children (5 percent) in the preschool-age group had an asthmatic event before baseline and 28,511 cases of asthma were recorded during follow-up. In the group of school-age children, 11,585 children (4.2 percent) had an asthmatic event during the seventh year of life.

Dog exposure during the first year of life was associated with a 13 percent decreased risk of asthma in school-age children. Farm animal exposure was associated with a 52 percent reduced risk of asthma in school-aged children and 31 percent reduced risk in preschool-age children respectively, the results indicate.

The authors note their results were independent of parental asthma or whether the child was first-born. Some study limitations were mentioned.

"For what we believe to be the first time in a nationwide setting, we provide evidence of a reduced risk of childhood asthma in 6-year-old children exposed to dogs and farm animals. This information might be helpful in decision making for families and physicians on the appropriateness and timing of early animal exposure," the study concludes.

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(JAMA Pediatr. Published online November 2, 2015. doi:10.1001/jamapediatrics.2015.3219. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editor's Note: Authors made conflict of interest and funding/support disclosures. Please see article for additional information, including other authors, author contributions and affiliations, etc.

Media Advisory: To contact corresponding author Tove Fall, Ph.D., email tove.fall@medsci.uu.se

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