The benefits of dog ownership are seemingly endless: They can be loyal companions, excellent running partners, and constant cuddle buddies.
Now, new research suggests that they may bring even more to the table. Children who grow up with dogs may be 15% less likely to develop asthma than kids who don’t, according to a new study published Nov. 2 in the journal JAMA Pediatrics.
Early exposures to farm animals, the study also found, add some immune-boosting benefits too.
Cases of childhood asthma have increased globally decade after decade. In fact, about 8% of children in the US suffered from the disease in 2013, according to the Centres for Disease Control.
Scientists have known about correlations between early exposure to animals and a reduced risk of asthma for a long time, but establishing a strong connection has been tricky. Small studies with limited numbers of people have turned up varying and sometimes contradictory results.
But the one constant is the inverse relationship between farm environment exposures and childhood asthma. A 2012 analysis of a large number of smaller studies found that children exposed to a farm environment have 25% less asthma prevalence than those who weren’t.
To probe whether this relationship held true for children who grew up with dogs — in addition to verifying previous findings about children exposed to farm animals — a team led by researchers from Uppsala University in Sweden combed through a massive registry of more than one million Swedish children born between 2001 and 2010.
Farm animal exposure, they found, was associated with a 52% reduced risk of asthma in six-year-olds and a 31% reduced risk in preschool-age children.
“Our results confirmed the farming effect,” Tove Fall, an epidemiologist at Uppsala University who co-authored the study, said in a press release.
When Tove and others adjusted the data for families who avoided dogs (e.g. because parents had asthma or their first-born children did), they found that children exposed to dogs within the first 12 months of life had a 15% reduced risk of developing asthma at the age of six.
Tove and others don’t know exactly why frolicking with Fido or farm animals early in life protects some kids from developing asthma. But their study points to the hygiene hypothesis: the idea that early exposure to a variety of microbes boosts our immune systems to fight an onslaught of germs and pathogens later in life. A dog might increase a young child’s overall exposure to microorganisms and allergens, helping her prevent allergy-related asthma from developing before she goes to school.
The additional exposure may not be all good news, though. According to the study, preschool-aged children who had dogs growing up also had a slightly higher risk of getting pneumonia and other respiratory tract infections — likely because of the additional exposure to germs.
The authors hope their results help families make decisions about whether and when to introduce their children to animals.
“[O]ur results are generalizable to the Swedish population, and probably also to other European populations with similar culture regarding pet ownership and farming,” Catarina Almqvist Malmros, a pediatrician at Astrid Lindgren Children’s Hospital in Stockholm and a study co-author, said in the release.
Given the size of the study, plus big pet and farming cultures here in the US, it’s probably not a stretch to assume Fido and farms could help protect American babies, too.