The Grapevine

Dog Ownership In The First Year Of Life Associated With Lower Risk Of Childhood Asthma

Dog and child
Owning a dog early on in your child's life may prevent them from developing childhood asthma, new research suggests. Tambako the Jaguar, CC BY-ND 2.0

Having a dog as part of your new family may help your child breathe a little easier in the future, new research suggests. The study, published Monday in JAMA Pediatrics, found evidence that children who spent their formative years with a dog in the household were less likely to develop asthma.

"Earlier studies have shown that growing up on a farm reduces a child's risk of asthma to about half. We wanted to see if this relationship also was true also for children growing up with dogs in their homes," said study author Dr. Tove Fall in a statement. "Our results confirmed the farming effect, and we also saw that children who grew up with dogs had about 15 percent less asthma than children without dogs." Fall is an assistant professor in epidemiology at the Department of Medical Sciences and the Science for Life Laboratory at Uppsala University in Sweden.

Fall and her colleagues analyzed the medical records of all Swedish children born from Jan. 1, 2001, to Dec. 31, 2010 (over one million) and cross-referenced it with information about their families’ medical history and pet/farm ownership in the first year of life, among other potential risk factors for asthma. They then observed the rates of asthma among preschool children from ages 1 to 5, as well as schoolchildren at age 6. "Because we had access to such a large and detailed data set, we could account for confounding factors such as asthma in parents, area of residence and socioeconomic status," Fall said.

Rates of asthma were similar between both age groups, hovering around 5 percent. though only about 8 percent of school children were exposed to dogs compared to around 14 percent of preschool aged children. Farm life was particularly protective against later asthma, with the risk of asthma cut by around half in both groups, but dog ownership offered a buffer as well. Notably, this preventive effect was similarly strong in children whose parents had asthma versus those who didn’t, as well as among first-born children.

"Our findings are in accordance with the hygiene hypothesis, which links a favorable maturation of the immune system with exposure to microbes in childhood," the authors wrote. "It has been shown that dog exposure is associated with altered bacterial flora in house dust and that mice exposed to such dust have alterations in their gut flora composition, as well as fewer allergic reactions."

Proving that hypothesis has been hard, however, with the authors noting that previous studies have found evidence for and against pet ownership as a risk factor for childhood asthma or other allergies. A 2012 review in PLOS ONE, for example, found that pet ownership (cat, dog, bird, or rodent) in the first two years of life "did not appear to either increase or reduce the risk of asthma or allergic rhinitis symptoms in children aged 6 to 10."

But the current authors believe that their study have a leg-up over previous research efforts, given the extensive amount of data available to them. Not only does Sweden’s nationalized health care system allow researchers to keep track of people’s health status throughout life, but Sweden also mandates every owned dog since 2001 to be registered, a universal step that other countries like the United States haven’t implemented as of yet, though many states like New York do. That, coupled with additional sources of information taken from other dog registries, allowed for more rigorous conclusions.

"These kind of epidemiological studies look for associations in large populations but do not provide answers on whether and how animals could protect children from developing asthma," said senior author Dr. Catarina Almqvist Malmros. "We know that children with established allergy to cats or dogs should avoid them, but our results also indicate that children who grow up with dogs have reduced risks of asthma later in life."

It appears, however, that more research will need to be done to validate their results stateside. "Thanks to the population-based design, our results are generalizable to the Swedish population, and probably also to other European populations with similar culture regarding pet ownership and farming,"  Almqvist Malmros added. 

Source: Fall T, Lundholm C, Ortqvist A, et al. Early Exposure to Dogs and Farm Animals and the Risk of Childhood Asthma. JAMA Pediatrics. 2015.

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