Deconstructing the Pet-Effect on Cardiovascular Health

BUFFALO, N.Y. -- Can the presence of Fido or Fluffy calm an owner's stress, as some studies have suggested? Or is the science as fuzzy as Fifi's coat?

Karen Allen, Ph.D., research scientist at the University at Buffalo, reviewed the scientific evidence to date relating to pets and cardiovascular responses in an article in the December issue of Current Directions in Psychological Science.

Her conclusion? Your beloved cat or dog can have a positive effect on your cardiovascular health, but don't stop taking your heart medicine.

In her article, "Are Pets a Healthy Pleasure? The Influence of Pets on Blood Pressure," Allen, who has conducted several studies on the health benefits of owning a pet, presented a broad picture of the findings and limitations in this area of research and suggested research directions that could answer important questions in the future.

Based on existing evidence, Allen concluded that a pet can be a positive factor in one's life, but that claims that "pets lower blood pressure" are simplistic and over-stated.

"Experimental studies looking at pets and responses to stress have focused on acute responses to stress, but other epidemiolgical studies have demonstrated an important role for pets," she said. "For example, there is clear evidence that having a pet (especially a dog) is associated with prolonged life after a heart attack.

"However, no prospective studies have explored if pets can help high-risk patients avoid a heart attack. The definitive study that remains to be done would follow high-risk people, some with pets, some without pets, over a period of years, and assess how they handle stress and if they have heart attacks."

In her review, Allen cited studies dating to 1980 that found a positive effect of a pet in various scenarios: on 1-year survival after a heart attack; on elders' visits to physicians; on depression in persons with AIDS; on blood pressure levels among children reading aloud, and on cardiovascular risk factors in general.

These and additional studies are grounded in the theory of the importance of social support, Allen noted. Many studies have highlighted the importance of support of friends in stressful situations, and have documented that owners who have formed a strong bond with their pets often characterize them as non-judgmental friends.

Allen's own studies involving tasks designed to be stress-inducing have shown that participants had lower heart rates and blood pressure during the tasks when in the company of their pets than when a spouse or close friend was present. In one experiment involving mental arithmetic, participants' blood pressure increased from an average of 120/80 to 155/100 with a spouse present, but increased only slightly, to 125/83, with a pet present.

The mechanisms behind these effects remain unclear, Allen said. The hypothesis that pets might provide a stress-relieving diversion from the task did not hold up. Participants performed faster and better in the presence of pets than spouses, Allen noted, likely due to the perceived "complete positive regard" of their pets.

The suggestion that the type of person who chooses to have a pet may have some inborn physiological advantage in times of stress also didn't hold up to scientific scrutiny, Allen noted. She described the findings of one of her own case-control studies designed to test this theory.

Participants were stockbrokers who lived alone, had never opted to own a pet, had self-described stressful lives and were due to begin drug therapy (ACE inhibitors) for high blood pressure. Half the participants were assigned randomly to adopt a dog or cat from an animal shelter, while half remained pet-free.

Results showed that ACE inhibitors successfully lowered resting blood pressure of all participants, but under stressful conditions, those assigned pets experienced half the increase in blood pressure of those without pets. The study also indicated that different mechanisms are involved in the regulation of resting and stress-induced blood pressure, with social support playing an important role in stressful situations.

The existing research has some limitations, in addition to the lack of long-term studies of pets and people at high risk of a heart attack, Allen noted.

No studies have been conducted on the potential of pets to increase stress, or on the physiological consequences of the death of a beloved pet, she said. In addition, little research has been done with pets other than cats and dogs, and no one has investigated the relationship of the pet effect and cultural, personal and demographic variables.