Growing up with a dog in the house during their first year of life could be of great benefit to children, by cutting their risk of asthma by as much as 15%. Using national data on more than a million children in Sweden, the researchers found that in addition to growing up with a dog, kids who grew up with frequent exposure to farms had an impressive 50% fewer cases of asthma. The results seem to support the idea that children growing up in households that are too clean could have an increased susceptibility to developing allergies.
“Earlier studies have shown that growing up on a farm reduces a child's risk of asthma to about half,” explained Tove Fall in a statement. Fall coauthored the study, published in JAMA Pediatrics. “We wanted to see if this relationship also was true also for children growing up with dogs in their homes. 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.”
The study was only made possible due to Sweden’s health care registration system. Each Swedish citizen has their own personal identification number which has to be used whenever a person seeks health care, with the data then placed in a national database, anonymized, and made available to researchers.
This mine of data was then combined with the dog ownership registration list, which has been in effect in Sweden since 2001, allowing the researchers to assess whether having a parent who owed a dog or who was registered as an animal farmer was associated with the likelihood of a child developing asthma. They found that for children who grew up in a household with a dog during their first year, the risk of them developing asthma by the age of six was reduced by 15%.
This study adds evidence supporting what is called the “hygiene hypothesis,” which states that a lack of early exposure to microbes and parasites as a child increases susceptibility to allergic reactions later in life. The researchers, however, point out that while they’ve found this association between growing up with a dog and a reduction in rate of asthma, the data cannot tell them the processes behind it.
“These kinds 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 Catarina Almqvist Malmros, senior author of the study. “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.”
Due to the large sample size, the researchers are confident that their results can be applied not just to the Scandinavian country, but also to other European countries with similar cultures regarding dog ownership.