Kramer and her colleagues reviewed data for more than 3.8 million people taken from 10 separate studies, and concluded that owning a dog is associated with a long-term lower risk of premature death.
But the Swedish study suggests that the companionship of a dog also contributes to a person’s health, said Dr. Dhruv Kazi, associate director of the Smith Center for Outcomes Research in Cardiology at Beth Israel Deaconess Medical Center, in Boston.
In the Swedish study, Dr. Mwenya Mubanga of Uppsala University and her colleagues combed their nation’s patient database for all people aged 40 to 85 who’d had a heart attack or stroke from 2001 through 2012.
The investigators identified more than 181,000 heart attack victims, about 6% of whom owned a dog, and nearly 155,000 stroke survivors, of whom 5% owned a dog.
Everyone who owned a dog had a reduced risk of death compared to those without a dog, but that risk was doubly reduced in people who lived alone versus those living with another person, the researchers found.
“My own hypothesis is that the biggest driver of this is what dog ownership does for one’s mental health,” said Kazi, who wrote an accompanying editorial about the two new reports.
Isolation and loneliness have been linked to poor heart health outcomes, Kazi said, and owning a dog appears to ease a person’s solitude enough to have a real benefit.
The Swedish study illustrates this. “Individuals living by themselves seemed to have the larger benefit, which goes in line with the fact that it’s the companionship driving a large chunk of this benefit,” Kazi said.
However, Kazi added that it would be a mistake to overlook the physical benefits of having a dog.
“If you own a dog, it doesn’t matter how tired you are or how cold out it is, you still have to go for a walk. That’s what you have to do,” Kazi said.