Dog ownership may improve outcomes, reduce mortality risk after CV events
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Now people may have another reason to love their dogs even more: Dog ownership was linked to improved outcomes after a major CV event and with a lower risk for death in the long term, according to two studies published in Circulation: Cardiovascular Quality and Outcomes.
“The findings in these two well-done studies and analyses build upon prior studies and the conclusions of the 2013 American Heart Association Scientific Statement ‘Pet Ownership and Cardiovascular Risk’ that dog ownership is associated with reductions in factors that contribute to cardiac risk and to cardiovascular events,” Glenn N. Levine, MD, professor of medicine at Baylor College of Medicine in Houston, director of the cardiac care unit at Michael E. DeBakey Medical Center in Houston and chair of the writing group of the AHA’s scientific statement on pet ownership, said in a press release. “Further, these two studies provide good, quality data indicating dog ownership is associated with reduced cardiac and all-cause mortality.”
Study on Swedish patients
Mwenya Mubanga, MD, PhD, assistant undergoing research training in the department of medical sciences, molecular epidemiology at Uppsala University in Sweden, and colleagues analyzed data from 181,696 patients with MI (mean age, 71 years; 64% men) and 154,617 patients with stroke (mean age, 73 years; 55% men) between 2001 and 2012 from the Swedish National Patient Register. Patients were aged 40 to 85 years and did not have an event between 1997 and 2001. Information on dog ownership was collected from two dog registers, as dogs are required to be registered in Sweden since 2001.
Death was the main outcome that was assessed in this study. A secondary outcome included rehospitalization for the same event after 30 days.
Dog ownership accounted for 5.7% of patients with MI and 4.8% of those with stroke.
During 804,137 person-years of follow-up for patients with MI, dog owners had a reduced risk for death after hospitalization, which was seen in those who lived alone (adjusted HR = 0.67; 95% CI, 0.61-0.75) and those who lived with a partner or child (aHR = 0.85; 95% CI, 0.8-0.9).
Similar results were seen for patients with ischemic stroke during 638,219 person-years of follow-up. The adjusted HR for patients who owned a dog and lived alone was 0.73 (95% CI, 0.66-0.8) and 0.88 for those who owned a dog and lived with a partner or child (95% CI, 0.83-0.93).
Dog ownership was also associated with a reduced risk for hospitalization for recurrent MI (HR = 0.93; 95% CI, 0.87-0.99).
“One mechanism may be an increased motivation for engagement in consistent physical activity in dog owners, a factor regarded important in post-event recovery of cognition, arm function, balance and gait,” Mubanga and colleagues wrote. “Another explanation is reduced risk of depression, an important risk factor for death after myocardial infarction.”
Systematic review, meta-analysis
In another study from the same publication, Caroline K. Kramer, MD, PhD, assistant professor in the division of endocrinology and metabolism at University of Toronto, and colleagues performed a systematic review and meta-analysis of data from 3,837,005 participants from 10 studies published between 1950 and May 24, 2019.
Studies were included if they included original data of prospective observational studies, included patients older than 18 years, reported CV mortality or all-cause mortality and evaluated dog ownership at baseline.
During a mean follow-up of 10.1 years, there were 530,515 deaths.
There was a 24% risk reduction for all-cause mortality in participants who owned a dog compared with those who did not (RR = 0.76; 95% CI, 0.67-0.86). Six studies showed a significant reduction in the risk for death in participants who owned a dog.
Participants with prior coronary events who lived in a home with a dog had an even more pronounced reduction in the risk for all-cause mortality (RR = 0.35; 95% CI, 0.17-0.69; I2 = 0%). When the analyses were restricted to studies that evaluated CV mortality, there was a 31% risk reduction for CV death in participants who owned a dog (RR = 0.69; 95% CI, 0.67-0.71; I2 = 5.1%).
“Taken together, our meta-analysis suggests the need for further investigation of the potential for dog ownership as a lifestyle intervention that may offer significant health benefits, particularly in populations at high risk for cardiovascular death,” Kramer and colleagues wrote.
Dhruv S. Kazi, MD, MSc, MS, associate director of the Richard A. and Susan F. Smith Center for Outcomes Research in Cardiology and director of the cardiac critical care unit at Beth Israel Deaconess Medical Center in Boston, wrote an editorial on both of these studies. “We should ... exercise extreme caution in extrapolating these results to other populations. However, given the magnitude of the potential benefit — and likely little or no harm — these findings should encourage clinicians to discuss pet adoption with their patients, particularly those with preexisting cardiovascular disease and those living by themselves,” he wrote. – by Darlene Dobkowski
References:
Kazi DS. Circ Cardiovasc Qual Outcomes. 2019;doi:10.1161/CIRCOUTCOMES.119.005887.
Kramer CK, et al. Circ Cardiovasc Qual Outcomes. 2019;doi:10.1161/CIRCOUTCOMES.119.005554.
Mubanga M, et al. Circ Cardiovasc Qual Outcomes. 2019;doi:10.1161/CIRCOUTCOMES.118.005342.
Disclosures: Levine, Mubanga and Kazi report no relevant financial disclosures. Kramer reports he received grants from Boehringer Ingelheim. Please see the studies for all other authors’ relevant financial disclosures.
Perspective
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Lynne T. Braun, PhD, CNP, FAHA, FPCNA, FAANP, FNLA, FAAN
Observational studies have shown that pet/dog ownership is associated with reduced CVD risk. It is unclear from previous research if there is a mortality benefit from dog ownership.
In the meta-analysis of 10 studies by Kramer, Mehmood and Suen, dog ownership was associated with a 24% reduction in risk of all-cause mortality and a 31% risk reduction for deaths due to CVD.
In an accompanying paper, Mubanga and colleagues hypothesized that dog ownership could improve outcome after a CV event, since it is associated with increased physical activity and greater social support. Using data from the Swedish National Patient Register, dog owners had a lower risk of death after hospitalization for acute MI or for ischemic stroke, which was more profound for those who lived alone compared with those living with a partner or a child. This implies that owning a dog provides a greater social support benefit for individuals living alone, which translates into improved CV outcomes.
When I read studies such as these, if it makes sense to the conversation I am having with my patient, I will often discuss study results. If my patient has pets or if I get the sense that my patient is socially isolated, I may discuss. If my patient is having a difficult time introducing physical activity in their life, I might discuss dog ownership.
Petting a dog (or cat) can be very soothing, force a person to relax and reduce stress. Dog companionship is associated with lower BP levels and improved lipid profiles, and also has been associated with reduced sympathetic nervous system responses to stress (less adrenalin and noradrenalin production). My medical center brings in dogs and miniature horses for stress reduction among the staff. Some scientific meetings are now doing the same for attendees.
The presence of this benefit may depend on the pet. Cats that snuggle up against a person and purr can be very soothing. It depends on the relationship a person has with their pets (dog, cat or whatever). Animals often show unconditional love if they are treated in a caring way.
Despite the “feel-good” nature of these studies, we cannot assume causation. As the authors of the meta-analysis point out, they could not control for factors that might impact mortality estimates such as overall health status and lifestyle factors (not smoking, regular exercise).
A randomized controlled trial would be needed to more precisely determine the impact of dog ownership on mortality and CV health. In the registry study evaluating dog ownership and survival after MI and stroke, it would be interesting to assess if dog ownership or companionship improves a patient’s engagement in the rehab process. Whether or not an individual owns a dog, perhaps if dogs were part of the rehab process, short- and long-term outcomes would benefit.
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