Dog Ownership and Control Of Borderline Hypertension: A Controlled Randomized Trial. Karen Allen, Ph.D.; Division of Clinical Pharmacology; Department of Medicine, Millard Fillmore Hospital; 3 Gates Circle, Buffalo, NY 14209; State University of New York at Buffalo. (Presented at the 22nd Annual Scientific Sessions of the Society of Behavioral Medicine in Seattle, WA; March 24, 2001).

Background and Participants

Previous research among people with drug-controlled hypertension has demonstrated that blood pressure reactivity to psychological stress can be lowered by the presence of the patient's pet. The current study explores if randomly assigned dog ownership can influence level of resting blood pressure as well as blood pressure reactivity. Included were 60 participants (30 male, 30 female) with borderline hypertension (average of 145/92), all of whom lived alone.

Study Design

Participants were randomly assigned to an experimental group (n=30) that agreed to adopt a dog from a shelter in month 1 of the study or a wait list control group (n=30) that agreed to adopt a dog after participation in a transcendental meditation program. In-home mental stress tests were conducted at months 1, 3, 6, 9, and 12 of the study. The stressors were mental arithmetic (increasingly difficult serial subtraction) and 4 different speech tasks. Ambulatory monitoring took place for 2 days in each of the data collection months. The dependent measures were Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), and Heart Rate (HR).

Results

The main analysis was repeated measures ANOVA. At the beginning of the study the experimental and control groups were not significantly different in any of the dependent measures. Mental arithmetic and speech tasks elicited significant increases in blood pressure among all participants (i.e., increases of > 40 mmHg in SBP). Two-day ambulatory monitoring revealed that participants had especially large increases in SBP while at work.

After 3 months the psychological stress tests as well as ambulatory monitoring were repeated. Participants with dogs present in their homes had significantly reduced resting BP (that is, to within the normal range), reactivity to stress, as well as ambulatory blood pressure, even while at work ( p < 0.001), while those in the transcendental meditation program exhibited no significant changes. Lowest ambulatory BP was recorded on the day participants took their dogs to work. This pattern of response was replicated 3 months after the control group acquired their dogs. These findings suggest that control of borderline hypertension can be assisted by a behavioral intervention involving a pet dog.

Discussion

As in our previous studies about the potential health benefits of pets, we believe that an explanation for our findings is that pets provide the type of nonevaluative social support that can buffer pathogenic responses to stress. In an effort to understand the relationships participants developed with their pets we held a post-study session in which the Nominative Group Technique was used to produce a consensus report of how they felt about their dogs. All participants voluntarily attended this session and the most frequently cited statement about the dogs was: "my dog makes me laugh, forget my worries, and see some of the best parts of life that I had been missing." No one would even think of parting with his/her dog at the end of the study. Since all the participants expressed fondness for dogs before the study began, we do not know if similar results would occur with participants who were not especially interested in having a pet.

Our previous work suggests that a strong bond between dog and person is necessary to elicit the diminished blood pressure responses we have found when people are in the presence of their pets. Interestingly, in the current study we found that the "pet effect" occurred during experimental stress even when dogs were not in the presence of their owners. We also found that the lowest (office) ambulatory blood pressures were found when the dogs were with their owners at work. Conclusion To our knowledge, this is the first controlled, randomized study to explore if borderline hypertension can be controlled with a pet dog, i.e., without drug therapy. We have demonstrated that dogs can indeed have a significant health effect on people who live alone and have borderline hypertension.

Study Timeline

Month 1

• MAT and Speech in home
• Ambulatory monitoring
• Experimental group adopts dogs

Month 3

• MAT and Speech in home: dogs present
• Ambulatory monitoring: dogs present
• Control group receives TM instruction

Month 6

• MAT and Speech in home: dogs not present
• Ambulatory monitoring: dogs not present
• Control group adopts dogs

Months 9 and 12

• MAT and Speech in home: dogs present for all participants
• Ambulatory monitoring: dogs present in home and office for all participants