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Dog owners live longer and fare better after a heart attack or stroke compared with those who have no canine companions, two studies published Tuesday suggest.
Researchers found that dog ownership was associated with a 24-percent reduced risk of death from any cause among the general public, and a 33 percent lower risk of death among heart attack survivors who live alone, according to the reports, published in the journal Circulation: Cardiovascular Quality and Outcomes.
The new studies are “interesting and provocative,” said Dr. Haider Warraich, director of the heart failure program at the Boston VA Healthcare System, an instructor at the Harvard Medical School and author of “State of the Heart: Exploring the History, Science and Future of Heart Disease.”
“I don’t think that this is what many people think about when adopting a dog,” said Warraich, who was not involved with the new research. “They think they’re doing it for the animal, not for their own health. But these studies suggest that adopting a dog may be as much of a service to your own health as the dog’s.”
Still, Warraich said, “it’s not enough to have me recommend patients adopt a dog to lower their risk of death.” For that to happen, there would need to be a lot more research, he noted.
One of the new studies merged data from the Swedish National Patient Register, which included information on all Swedes from the ages of 40 to 85 who had had a heart attack or stroke between January 2001 and December 2012, with data from the Swedish Kennel Club and the Swedish Board of Agriculture dog registers.
Out of those databases, the researchers gathered information on 181,696 patients who had had a heart attack, 5.7 percent of whom owned a dog, and 154,617 who had had a stroke, 4.8 percent of whom had a dog.
After accounting for factors such as age, other health issues, marital status, the presence of children in the home and income, the researchers found that heart attack survivors who lived alone had a 33 percent lower risk of death in the year after their heart attack if they had a dog, compared with non-dog owners. Among those who did not live alone, the reduction in risk was smaller, at 15 percent.
And that may be a clue to explaining how dogs might help their owners live longer.
“We know that loneliness and sedentary lifestyle is a major risk factor for premature death,” said study co-author Tove Fall, a professor of molecular epidemiology at Uppsala University in Sweden. “Dogs are an excellent motivation for their owners to get outdoors and walk them.”
Four-legged friends can also be a source of social support. “Dog-owners are also reported to have more social interaction with other humans,” Fall said.
The second study, which included information on 3,837,005 people, looked at data from 10 earlier studies. Researchers found that, among the general population, dog owners had a 24 percent lower risk of death from any cause over an average follow-up period of 10 years, compared with non-dog owners. Among dog owners with cardiovascular disease, the risk was 65 percent lower.
The results weren’t a surprise, said the study’s lead author, Dr. Caroline Kramer, an endocrinologist and clinician scientist at the University of Toronto’s Mount Sinai Hospital. A lot of smaller studies, including some that randomized people to either adopt a dog or not, have shown that having a canine companion can lower blood pressure, improve cholesterol and reduce the risk of depression, Kramer said.
What sets dogs apart from other pets, in terms of health benefits for humans, is their need to go for walks, Kramer said.
“As a dog owner myself I can see the benefits,” she added. “My step counting really went up after I got a dog.”
While the studies don’t prove that dog ownership leads to longer lives — they can only show associations, not causation — there have been studies showing that the companionship of a dog can lower levels of the stress hormone cortisol, said Neda Gould, an assistant professor and director of the Mindfulness Program at the Johns Hopkins School of Medicine.
“When the stress response is turned on too frequently, it leads to a lot of wear and tear on the body in general,” Gould said.
For those who are worried that a dog might be too much responsibility, experts suggest starting with a low-maintenance pet — like goldfish, perhaps. Even those kinds of pets can provide a benefit, albeit a smaller one. In fact, an earlier study showed that just caring for crickets could make people healthier.
Part of what the researchers are seeing in the new studies might be tied to the care owners give to their dogs, said Stewart Shankman, a professor and chief psychologist at Northwestern University’s Feinberg School of Medicine.
“There are mental health benefits that come from altruism, for taking care of somebody besides yourself,” Shankman said.