Does pet ownership reduce your risk for heart disease? Originally published in InterActions, Vol. 10, No. 3, 1992, pp 12-13.
Do you exercise, watch your diet or take medication to lower your blood pressure, blood fats and cholesterol levels? If you do, maybe you should also get yourself a pet. New research confirms and expands earlier studies indicating a link between pet ownership and a reduced risk of developing heart disease.
Results of a three-year study of 5,741 people at the Baker Medical Research Institute, Melbourne, Australia, show that pet owners had lower blood pressure and triglyceride and cholesterol levels than did non-owners-a result that could not be explained by such personal differences as cigarette smoking, diet, weight or socioeconomic profile. Even the researchers were surprised by the results. Dr. Warwick Anderson, principal research fellow and associate director of the institute, admits that those involved considered such an outcome "an unlikely hypothesis" prior to the study. "First of all, we were a bunch of cynics. When you're a scientist, you're used to questioning things. Then, when you think of all the things that can affect cardiovascular risk factors, I guess we felt it unlikely that something this subtle [pet ownership] would show up, and if it did, any effect was likely to be small. That's why we studied so many people." It was impressive for us that all the risk factors were lower in pet owners. We feel a bit differently now than we did a few years ago about the hypothesis," says Dr. Anderson.
The Baker Institute is Australia's major heart and vascular disease research institute, associated with the Alfred Hospital in Melbourne. The institute conducts a wide range of research on the cardiovascular system and its diseases. This was the first study at the institute to consider the effects of pet ownership on heart disease, according to Dr. Anderson, although they have always been interested in ways of treating heart disease without drugs. "In this study we didn't think we'd see anything, but we were looking at it as another non-pharmacological way of addressing heart disease."
The institute's president, Sir Laurence Muir, had suggested the research after reading of another study that showed a lowering of blood pressure after petting a dog. Dr. Anderson says those at the institute considered it a challenge to see if there were any long-term, rather than momentary, effects associated with such interactions. He says that the Australian medical community has received the research results quite positively and that the Australian Heart Foundation has also supported the findings. "We thought that our colleagues would give us a stir about this, but they are supportive." The research was also received with enthusiasm when Dr. Anderson presented the results at the 6th International Conference on Human Animal Interactions in Montreal. The paper, by Drs. Anderson, Christopher Reid and Garry Jennings. has been published by the Medical Journal of Australia.
The study was conducted with men and women ages 20 to 60 from December 1987 to December 1990. Subjects had no idea prior to arrival at the clinic that they would be involved in research dealing with pet ownership. All had come to attend a heart disease risk assessment clinic at the institute. Most participants were from the nearby suburbs which are of mixed socioeconomic profile, but there were also people from other areas of greater Melbourne. To ensure that a representative sample of the population was studied, local industrial, community and service groups were given notices about the clinic.
To determine their risk for heart disease, each person was asked to fill out a lifestyle questionnaire about their diet, exercise and smoking habits, alcohol consumption and their personal and family history of heart disease. Subjects were also asked to provide demographic details and their socioeconomic status was determined.
During their clinical examination, two blood pressure measurements were taken, a blood sample was drawn and the concentrations of cholesterol and triglycerides were measured. Height and weight were also recorded and all data were entered into a computer. Participants' results were then explained to them. It wasn't until this point that people were told about the survey on pet ownership. After all clinical work was done, each person was asked if he or she owned a pet, and if so, they were asked to complete another brief questionnaire. Of the 3,394 men and 2,347 women engaged in the study, 784 reported that they owned one or more pets. The results showed that 476 owned dogs, 421 owned cats, 136 owned a bird, 106 owned fish, 28 owned horses and 48 owned other kinds of animals.
When the results for all pet owners were combined, they showed significantly lower triglyceride and cholesterol levels as well as lower systolic blood pressure readings for pet owners than for non-owners. The results were less marked for women, although female pet owners over 40 showed a significantly lower systolic blood pressure than did non-owners. This corresponds to the age at which heart disease becomes a leading cause of death for Australian women. When examining these results, researchers tried to determine if there was some factor other than pet ownership that was influencing the outcome. For example, they thought that pet owners may have come from a higher socioeconomic group, which would have lowered their risk profiles. Not so. The data showed that pet owners and non-owners came from very similar backgrounds with almost identical family incomes and similar educational qualifications.
A look at lifestyle risk factors also failed to turn up any evidence that could have influenced the findings. In fact, the results were somewhat confounding. Pet owners reported that they were more active, but that they also drank more alcohol and ate more take-out food. Pet owners and non-owners reported similar habits with regard to smoking and egg and salt intake. Likewise, there were no real differences in both groups' body mass index for either men or women.
Although the researchers are cautious about saying that pet ownership alone can lower the risk factors for heart disease, they do admit that it may have some effect. They say that their study's significance is that it will stimulate more research on the topic. Dr. Anderson reports that the Baker Research Institute has already started a case control study that will more thoroughly examine pet ownership in people with and without heart disease. This study is expected to run through 1993. In addition, the institute in 1993 will begin a long-range study of individuals before and after they acquire a pet. Meanwhile, pet owners can look at their animal companions with even greater appreciation for the ways they enrich their lives.
