Here’s some tail wagging-ly good news for dog owners: People who own a dog tend to live longer and are less likely to die early of heart disease than those who do not own a dog, according to a Canadian study published this month in the journal Circulation: Cardiovascular Quality and Outcomes.
A second study — a meta-analysis conducted by Swedish researchers and published in the same journal — found that owning a dog is associated with an additional positive health outcome: a longer life after a heart attack or stroke. That benefit was particularly strong for people who live alone.
These studies weren’t designed to determine why having a canine pet may be linked to a healthier heart and a longer life, but other research has suggested a variety of factors — most notably the daily walks that dogs demand of their owners.
After all, exercising a dog exercises the owner, too.
“But the most salient benefits of dog ownership on cardiovascular outcomes are likely mediated through large and sustained improvements in mental health, including lower rates of depression, decreased loneliness, and increased self-esteem,” writes Dr. Dhruv Kazi, a cardiologist at the University of California, San Francisco, in an editorial that accompanies the studies.
“This may explain why the effect appears to be larger for individuals living alone than those in multiperson households,” he adds.
The Canadian study was a systematic review and meta-analysis of pooled data from 10 separate studies involving 3.8 million people from the United States and seven other developed countries. The studies followed people for an average of 10 years.
The researchers analyzed that data to see if people who owned dogs had a higher or lower risk of death from any cause — and, more specifically, of death from a cardiovascular “event” such as a heart attack or stroke — than people who didn’t own dogs.
The analysis revealed that dog owners were less likely to have died during the studies’ follow-up periods than people who didn’t own dogs.
Specifically, they were 24 percent less likely to have died of any cause and 31 percent less likely to have died of cardiovascular disease.
Among dog owners with a history of heart attack, the decline in risk was particularly strong. Compared to non-dog owners with a similar medical history, they were 65 percent less likely to have died during the studies’ follow-up periods.
“Our meta-analysis suggests that dog ownership warrants further investigation as a lifestyle intervention given the positive association with longer survival,” the researchers conclude.
A cohort study
The Swedish study was a cohort study, a type of research that follows a group of people (the cohort) over a period of time to see if certain factors in their lives are associated with one or more health outcomes. In this case, the cohort was a database of all Swedish people aged 40 to 85 who had experienced a heart attack or stroke between January 2001 and December 2012. The factor examined was dog ownership and the health outcome was survival after a heart attack or stroke.
About 337,000 individuals fell into the study’s cohort, and around 5 percent of them owned a dog. (The researchers were able to pin that percentage down with some accuracy because Sweden requires all dogs to be registered.)
The researchers then looked to see if the people who had died within an average of four years after their heart attack or stroke were more or less likely to have been dog owners. They found that dog owners were 21 percent less likely to have died after a heart attack and 18 percent less likely to have died after a stroke than people without a dog.
The lower risk was particularly strong for people living alone with a dog. They were 33 percent less likely to die after a heart attack and 27 percent less likely to die after a stroke than people living alone without a dog.
All those reductions in risk were calculated after the researchers took into account several confounding factors that are known to affect recovery from a stroke or heart attack, such as age, gender, income and previous history of cardiovascular events.
“The results of this study suggest positive effects of dog ownership for patients who have experienced a heart attack or stroke,” said Tove Fall, the study’s senior author and a professor at Uppsala University in Sweden, in a released statement. “However, more research is needed to confirm a causal relationship and giving recommendations about prescribing dogs for prevention.”
Limitations and implications
These studies come with a huge caveat. They are based on observational research, so they don’t prove that dog ownership has a positive effect on health. Other differences between dog owners and non-dog owners may explain the studies’ findings.
Indeed, as Kazi points out in his editorial, “pet owners tend to be younger, wealthier, better educated, and more likely to be married, all of which improve cardiovascular outcomes.”
These studies adjusted for many of these “confounding factors,” but they weren’t able to identify and account for all of them.
Kazi also notes that the association between dog ownership and better health could be “because adults with excellent physical health are more likely to adopt a dog than those who are too ill or frail to care for a pet” — a phenomenon known as reverse causation.
Still, the findings from these two studies are intriguing. They also support the American Heart Association’s position that dog ownership may be helpful in reducing cardiovascular risk.
That organization emphasizes, however, that “the adoption, rescue, or purchase [of a dog] should not be done for the primary purpose of reducing cardiovascular disease risk.”
Kazi concurs. “Adopting a dog is a much larger undertaking than embarking on a new medical therapy,” he points out. “Adding a 4-legged member to the family involves long-term commitment and often substantial lifestyle changes.”
“Although a growing body of evidence now supports the idea that adopting a dog enhances the mental and physical well-being of its human companion, the real reward of dog ownership, in the words of Pulitzer Prize-winning poet Mary Oliver, is that there can hardly be a “sweeter arrangement” than the unconditional love of a loyal friend,” Kazi adds. “The health benefits of dog ownership are a welcome and possible substantial bonus.”
FMI: You can read both studies and the editorial on the website for Circulation: Cardiovascular Quality and Outcomes.