"Fido, sit. Fido, shake. Fido, reduce asthma risks for children. Good boy."
The study, published in JAMA Pediatrics, was conducted by researchers in Sweden, in a joint partnership between Karolinska Institutet and Uppsala University.
According to the study authors, childhood asthma is a global health concern that has been on the rise over the past 30 years. In the US, 9.3% of children currently have asthma, a chronic disease that affects the airways.
People who suffer from asthma have airways that are sore and swollen. If left untreated, children with the condition often have less stamina and tend to avoid physical activities in order to prevent coughing or wheezing.
Previous studies have linked certain environmental factors with either increased or decreased risks of asthma, including tobacco smoke exposure, dog and cat contact, family size, birth order, exposure to microbes and socioeconomic factors.
To further investigate, Tove Fall, PhD, of Uppsala University, and colleagues studied the link between animal exposure and asthma incidence in the Swedish population, which included over 1 million children born between 2001-2010.
Dogs present kids with more exposure to diverse microorganisms
Although the link between early life dog contact and subsequent asthma development has been studied before, the researchers say findings have not been conclusive.
Fast facts about childhood asthma
- In the US, over 6.8 million children have asthma
- In total, 9.3% of children in the country have the condition
- Kids with asthma often complain their chest hurts or that they cannot catch their breath.
"Earlier studies have shown that growing up on a farm reduces a child's risk of asthma to about half," explains Fall. "We wanted to see if this relationship was true also for children growing up with dogs in their homes."
In their analysis, the team used registry data for information on dog and farm animals, and for asthma medication and diagnosis in both preschool-age and school-age children.
Of the children included, 5% of the preschool-age children had an asthmatic event before baseline, and there were 28,511 cases of asthma observed during follow-up. Meanwhile, in the school-age children group, 4.2% had an asthmatic event at age 7.
Results show that dog exposure during the first year of life was linked with a 13% lower risk of asthma when the child was school-aged. Additionally, farm animal exposure was linked with a 52% reduced risk of asthma in school-age children and a 31% reduced risk in preschool-age children.
The researchers explain that children living on a farm - and children who live with a dog - come into regular contact with "elevated amounts and diversity of microorganisms and endotoxins."
Exposures like this "have the potential to influence the risk of asthma as well as the burden of infectious disease," they say, concluding:
"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."
Study strengths and limitations
To the researchers' knowledge, theirs is the largest study to date that allows for stratification on parental asthma. Adding in the fact that they had access to a "rich set" of possible confounders, their study has many strengths.
There were, however, some limitations. One, for example, is that the team could not account for animal exposure outside the home or visiting dogs.
Additionally, due to the availability of health registers, the researchers could only study school-aged children while they were 7 years old, which means that older children were not included.
Still, the large study population size makes their findings particularly strong. "Thanks to the population-based design," says senior author Dr. Catarina Almqvist Malmros from Karolinska, "our results are generalizable to the Swedish population, and probably also to other European populations with similar culture regarding pet ownership and farming."
Medical News Today recently reported on another study outlining more positive effects of dog ownership. According to new research, therapy dogs have a calming effect on children with cancer.