Heart's Best Friend? Dog Owners Have Longer Life Expectancy After Coronary Events

Julia Rommelfanger

October 21, 2019

A dog is not only man's best friend. Companionship from a dog may also have a positive effect on an owner's cardiovascular health, even lengthening their life span, according to research.

This is the essence of a prospective study and a meta-analysis looking at the cardiovascular risks and survival of dog owners.

"These two studies provide good, quality data indicating dog ownership is associated with reduced cardiac and all-cause mortality," commented Dr Glenn Levine, chair of the Working Group responsible for writing the official statement from the American Heart Association (AHA) on pet ownership. "While these non-randomised studies cannot 'prove' that adopting or owning a dog directly leads to reduced mortality, these robust findings are certainly at least suggestive of this," he continued.

Based on previous studies, which had shown that social isolation and an inactive lifestyle have a negative impact, researchers wanted to establish to what extent dog owners would get health benefits from the companionship of their four-legged friends.

Meta-analysis Finds Associations With Lower Mortality Rate

In a meta-analysis, researchers in Canada analysed 10 studies with a follow-up of 1 to 22 years; most of them from Scandinavia and England, in which the connection between dog ownership and mortality rates was investigated.

Previous research has shown that dog owners have lower blood pressure and better cholesterol values, implying better heart health. However, it was unclear if dog ownership is associated with improved survival, as previous studies have yielded inconsistent results, according to the team of authors led by Dr Caroline Kramer of Mount Sinai Hospital and University of Toronto.

The analysis was based on data from more than 3.8 million patients from 10 prospective studies. Nine of them compared all-cause mortality of dog owners and non-owners, and four studies compared cardiovascular outcomes. The results showed that dog ownership was associated with: 

  • 24% reduction in overall all-cause mortality

  • 65% reduction in all-cause mortality in individuals who had prior coronary events

  • 31% reduction in cardiovascular mortality

"Our findings suggest that having a dog is associated with longer life", said Dr Kramer, herself a dog owner, in a news release. Although confounding factors such as better fitness or a healthier lifestyle were not taken into consideration in the analysis, the results appear to be "very positive", she said.

"The next step on this topic would be an interventional study to evaluate cardiovascular outcomes after adopting a dog and the social and psychological benefits of dog ownership."

Dog Benefits for People Living Alone 

In the other study, Dr Mwenya Mubanga and a team of researchers from Upsala University in Sweden used data from the Swedish National Patient Register to conduct a prospective study on the survival of dog owners compared with non-owners following a major cardiovascular event between 2001 and 2012. The register identified 181,696 heart attack patients, 5.7% of whom were dog owners, and 154,617 stroke patients, 4.8% of whom were dog owners.

Results showed that the chances of survival for those owning a dog were clearly better; especially for dog owners without a partner or children. Dog owners who lived alone had a 33% lower risk of death after hospitalisation for myocardial infarction compared with non-owners, while those who lived with a partner or child were at 15% lower risk compared with heart attack patients without a dog.

Similarly, after an ischaemic stroke, dog owners who lived alone had a 27% lower mortality risk compared with non-owners, while for patients living with a partner or child the risk was 12% lower.

Dog ownership may be particularly important in single-occupancy households, both to provide motivation for physical activity and for substitute companionship, the authors speculate.

"We know that social isolation is a strong risk factor for worse health outcomes and premature death," said principal investigator Prof Tove Fall from Uppsala University. "Furthermore, keeping a dog is a good motivation for physical activity, which is an important factor in rehabilitation and mental health."

Dogs & Longevity

In a companion editorial in Circulation , Dr Dhruv Kazi from Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, US, said: "Dogs offer companionship, reduce anxiety and loneliness, increase self-esteem, and improve overall mood."

To date, the effect on physical health had been less clear, he said. Now, both of these studies have yielded positive findings. However, the question remains as to whether the results represent a causal correlation or merely an association. "Of course, what we really care about is not whether dog ownership is associated with improved survival but whether dog ownership results in improved survival," Dr Kazi writes.

In his opinion, the observed association is certainly real: the survival advantage has been shown in multiple countries and in diverse populations, so an incidental finding is unlikely.

Pet owners tend to be younger, wealthier, better educated, and more likely to be married, all of which improve cardiovascular outcomes; however in the Swedish study the correlation remained after taking into account potential demographic and socioeconomic confounding factors.

A connection between owning a dog and improved cardiovascular health due to more exercise, spending more time in the fresh air and less stress may be "biologically plausible", he believes. However, above all, improved mental health from owning a dog may have the most salient impact on cardiovascular outcomes. "My interpretation of the collective evidence to date is that the association between dog ownership and improved survival is real, and is likely at least partially causal."

Translated and adapted from Medscape's German Edition .

Pet Ownership and Cardiovascular Risk. A Scientific Statement From the American Heart Association.

Mubanga M, et al: Circulation: Cardiovascular Quality and Outcomes 2019;12:e005342

Kramer C, et al: Circulation: Cardiovascular Quality and Outcomes 2019;12:e005554

Kazi DS: Circulation: Cardiovascular Quality and Outcomes 2019;12:e005887


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