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Ezra, a 6-year-old dog, stands at the end of the Blessing of the Animals during St. Francis Day at St. Ann & the Holy Trinity Church, Sunday, Oct. 6, 2019, in the Brooklyn borough of New York.

Some tips for living a long, healthy life: Eat right. Get plenty of sleep and exercise. And get a dog.

That last item comes courtesy of a new study published in Circulation, the journal of the American Heart Association, which reviews several decades’ worth of evidence on the relationship between dog ownership and mortality.

The authors undertook the review in an effort to reconcile differences in previously published literature on the topic, some of which showed a benefit to dog ownership, others which did not.

After reviewing 10 studies that included data on 3.8 million participants, the authors determine that “dog ownership was associated with a 24% risk reduction for all-cause mortality as compared to non-ownership.” The data showed even greater benefits among those who’d experienced cardiovascular issues, such as a heart attack and stroke.

“Dog ownership,” the authors conclude, “is associated with lower risk of death over the long term, which is possibly driven by a reduction in cardiovascular mortality.”

So what exactly is it about owning a dog that would make people live longer?

In an accompanying editorial, cardiologist Dhruv Kazi of Beth Israel Deaconess Medical Center outlined some of the findings. For starters, there are well-documented mental health benefits to owning a pooch: “Dogs offer companionship, reduce anxiety and loneliness, increase self-esteem, and improve overall mood,” Kazi writes. The 2018 General Social Survey, for instance, found that dog owners were happier than cat owners.

Then there are the physical benefits. “Several studies have shown that acquiring a dog perforce increases physical exercise (as anyone who has unsuccessfully tried to sleep past the time of a dog’s routine morning walk can attest),” Kazi writes. People who own dogs tend to spend more time outdoors, which is known to be beneficial to health. Simply petting a dog — especially a familiar one — lowers a person’s blood pressure.

It’s plausible that such physical and mental health benefits are the pathway by which dog ownership makes a person live longer. One drawback in the literature, however, is that there haven’t been any randomized controlled trials looking at dog ownership and mortality. Researchers haven’t done many studies, for instance, that direct one group of people to purchase a dog, and another group to remain petless, and track their health over a period of time. Those types of studies are considered the gold standard of evidence, what you’d need to be able to say definitively that owning a dog causes people to live longer.

You’d want to do this to rule out confounding factors. “Pet owners tend to be younger, wealthier, better educated, and more likely to be married, all of which improve cardiovascular outcomes,” Kazi writes. It may be the case that being healthier and wealthier causes people to be more likely to acquire a dog.

Still, Kazi writes, the balance of the evidence to date convinces him that “the association between dog ownership and improved survival is real, and is likely at least partially causal.” One of the larger studies included in the review controlled for a variety of socio-economic and demographic factors and found that the longevity effect of dog ownership remained.

There also have been several randomized controlled studies on pet ownership in general, showing direct benefits of owning an animal. In one, a group of cardiac patients who had been randomly instructed to acquire a dog or a cat showed a diminished blood pressure response to stressful situations. In another, researchers randomly assigned nursing home residents in Korea pet crickets and directed them to care for the insects for eight weeks. After that time, the cricket-caring group showed significant improvements on measures of depression and cognitive ability, relative to the control group.

“The most salient benefits of dog ownership on cardiovascular outcomes,” Kazi writes, “are likely mediated through large and sustained improvements in mental health, including lower rates of depression, decreased loneliness, and increased self-esteem.”

Though the current study didn’t examine the effects of cat ownership on mortality, at least one previous paper has explored the connection and found that cat ownership, too, is linked to a decrease in fatal cardiovascular events.

That suggests that if you’re really serious about living a long life, you should get a dog and a cat to cover all your bases.

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