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.
