Dog owners who live alone have a 36 percent lower risk of death from cardiovascular disease than those without dogs. When it comes to dog owners who live with family members, the risk decreases by 15 percent.
"A very interesting finding in our study was that dog ownership was especially prominent as a protective factor in persons living alone, which is a group reported previously to be at higher risk of cardiovascular disease and death than those living in a multi-person household," Mwenya Mubanga, a study author and PhD student at Uppsala University in Sweden, told CNN.
Published in “Scientific Reports,” the study was conducted by researchers in Sweden who examined medical and pet ownership records of 3.4 million people. Those analyzed by the study were between 40 and 80 years old. Participants were followed for up to 12 years, with around 13 percent owning pet dogs.
Researchers also noted that individuals who owned dogs originally bred for hunting, such as terriers, retrievers and scent hounds, saw even greater benefits. It's unclear exactly why this is, but researchers suggest that these breeds require more exercise, meaning the owner is necessarily more active and healthier.
However, while the study clearly shows correlation between dog ownership and better heart health, it may not necessarily prove causation.
"These kind of epidemiological studies look for associations in large populations but do not provide answers on whether and how dogs could protect from cardiovascular disease," Tove Fall, a professor at Uppsala University and senior author of the study, told the BBC.
"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."
At the same time, previous research has also pointed to the positive health benefits of owning dogs. For example, one study showed that children with dogs at home had a 15 percent reduced risk of asthma. Authors of that study suggested this was due to the "hygiene hypothesis," which posits that too clean of an environment actually increases an individual's susceptibility to allergies.
In fact, the authors of the new study also said a possible reason for the positive effect of dogs on the heart may be connected to bacteria. According to the researchers, dogs actually change the dirt in their owners’ environment, meaning they may also influence their owner's bacterial microbiome. This collection of microscopic species lives in the gut and may benefit cardiovascular health.
But perhaps the biggest factor the research points to is the social aspect of owning a dog.
"[Dog ownership] may encourage owners to improve their social life, and that in itself will reduce their stress level, which we know absolutely is a primary cause for cardiovascular disease and cardiac events," Dr. Rachel Bond, associate director of women's heart health at Lenox Hill Hospital in New York, told CNN.
And of course, dogs definitely increase an individual's overall happiness.