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A new report by a task force of the American Heart Association has put out the message that owning a dog may protect you from heart disease.
Those of you who have followed this blog know that my primary interests include the behavior of dogs and our psychological bond to our pets. In it I often talk about how dogs affect our mental health (for example see here) but since I am a psychologist it is understandable that I talk less frequently about how dogs affect our physical health—although sometimes I report interesting material on that topic (for example see here or see here). For that reason, three or four times each year I make a systematic search of the major physical health related scientific journals to see if anything new and exciting has come out. This time my search revealed something which I believe was overdue, but nonetheless unexpected.
The American Heart Association (AHA) is the largest cardiovascular health organization in America, and it occasionally convenes a panel of experts to review data on particular procedures, drugs, health regimes, and various technical matters having to do with heart health and care. The reports of these panels are usually published in the principal journal of the organization Circulation. These reports are noted for being quite detailed and are often quite conservative and cautious in their conclusions. One of the AHA's most recent reports reviewed dozens of studies and concluded that pet owners, especially those with dogs, were in better health than people without pets (see here). For example the panel cited an Australian study of 5741 participants attending a free screening clinic which found that dog owners had significantly lower blood pressure.
Since the panel was primarily comprised of physicians and surgeons, its bias was to look for physical factors associated with dog ownership that might produce the health benefits. One of the emphases was to focus on the fact that people who own dogs certainly have more reason to get outside and take walks. Thus the report noted that in a study of more than 5,200 adults, dog owners engaged in more walking and physical activity than non-dog owners, and were 54% more likely to get the recommended level of physical activity. In support of the idea this increased exercise might be the link to the health benefits of dogs the panel cites an observational study of 2199 subjects which found that among those who walk their dogs the rate of obesity was 17%, compared to non-pet owners at 22%, and perhaps most significantly, dog owners who did not walk their dogs who had her obesity level of 28%. The panel therefore leans toward the view that it is the increased exercise associated with owning a dog that is the most important factor. I mentioned this conclusion to a colleague of mine at our medical school and he muttered "In an ideal society, where people are actually listening to their doctors' 'recommendations to be more active you wouldn't need dogs to drag people outside to move around a little bit."
However the committee did not ignore the data dealing with the mind-body links to our health. They did acknowledge the studies which show that most owners form such close bonds with their dogs that being in their presence actually blunts the owner's reaction to stress, lowering their heart rate, reducing the level of stress hormones in the blood, and thus helping to protect the cardiovascular system.
Dr. Glenn N. Levine, a professor at Baylor College of Medicine and the head of the committee that wrote the statement, was careful in describing the panel's conclusions. “We didn’t want to make this too strong of a statement, but there are plausible psychological, sociological and physiological reasons to believe that pet ownership might actually have a causal role in decreasing cardiovascular risk.”
The reason for his caution is that the vast majority of studies looking at the health benefits of dogs are correlational in nature. To put this simply, in a non-technical manner, such studies report that people who own dogs tend to be in better health than people who do not. The problem here is that although we might like to conclude that this means that if you own a dog you will be in better health, we are really looking at an association between two bits of data, not necessarily anything having to do with cause and effect. For example, it might just as well be the fact that it is people who are in better health who are more likely to bring a dog into their home as a pet.
However there is more research involving what scientists call "randomized controlled studies" which has been emerging recently and the findings from such studies tended to tip the balance in favor of accepting the fact that dog ownership had health benefits for humans. One example that the panel cites is a study of 48 stockbrokers whose jobs with them under high stress and all of whom showed symptoms of hypertension. These individuals were put on a medication that lowered their blood pressure, and then researchers divided them into groups. Those in one group were told to adopt a dog or cat. Six months later the researchers found that when the stockbrokers who had adopted pets were around their new companions they were remarkably calm her in the face of stressful events than the stockbrokers without pets and showed greatly reduced stress related physiological responses.
In discussing the overall conclusions of their report Dr. Levine noted that the more traditional methods of risk reduction for heart disease have now been proven to be effective and to the AHA it seemed like this was a good time to investigate alternative approaches to heart health—such as dog ownership. He said, "We felt that this was something that had reached the point where it would be reasonable to formally investigate the issue." And the conclusion of their investigation is that pet ownership, particularly dog ownership, is probably associated with decreased cardiovascular disease risk.
However, Dr. Levine remains cautious in this conclusion pointing out that he and his colleagues were not recommending that people adopt pets for any other reason than to give them a good home. He said, “If someone adopts a pet, but still sits on the couch and smokes and eats whatever they want and doesn’t control their blood pressure, that’s not a prudent strategy to decrease their cardiovascular risk.”
Stanley Coren is the author of many books including: The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; The Left-hander Syndrome
Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission
