A team of researchers at Uppsala University tracked the health and dog ownership status of more than 3.4 million Swedes aged 40 to 80 years old for 12 years, starting in 2001. No one involved had a history of cardiovascular disease.
Everyone in Sweden must carry a unique personal identification number, all hospital visits are recorded, and dog ownership registration is mandatory, which makes it the perfect case study for this sort of experiment. As the researchers point out, however, the results can be generalized to all other countries with a similar culture towards dog ownership (including other European countries and the US).
The researchers found that dog owners were less at risk of dying from cardiovascular disease and other causes. If they owned a pure breed, that is. The results were less clear for those who owned mixed-breeds.
On average, people's risk of death in a multi-person household was reduced by 11 percent, with their risk of dying from a cardiovascular disease decreased by 15 percent. The health benefit was even more pronounced in single-person households.
“Perhaps a dog may stand in as an important family member in the single households," Mwenya Mubanga, lead junior author of the study and PhD student at the Department of Medical Sciences and the Science for Life Laboratory at Uppsala University, explained in a statement. "The results showed that single dog owners had a 33 percent reduction in risk of death and 11 percent reduction in risk of myocardial infarction during follow-up compared to single non-owners."
So why does owning a dog seem so good for you? The study revealed a correlational relationship between dog ownership and longer lives, but didn't explore the reasons behind it. The researchers do, however, offer some possible explanations.
“We know that dog owners in general have a higher level of physical activity, which could be one explanation to the observed results,” Tove Fall, senior author of the study and associate professor in Epidemiology at the Department of Medical Sciences and the Science for Life Laboratory at Uppsala University, said in a statement.
This is backed up by the fact that hunting dogs like terriers, retrievers, and scent hounds need more exercise. “Other explanations include an increased well-being and social contacts or effects of the dog on the bacterial microbiome in the owner," Tove added.
Tove also notes, however, some limitations of the study: "There might also be differences between owners and non-owners already before buying a dog, which could have influenced our results, such as those people choosing to get a dog tending to be more active and of better health.”