Having a pet appears to help buffer against the physiological consequences of chronic exposure to stress. But, according to new research, the link between pet ownership and reduced allostatic load depends on certain socioeconomic factors, such as ethnicity. The findings have been published in SSM – Population Health.
Allostatic load refers to the cumulative physiological wear and tear on the body that results from chronic exposure to stressors. It is a concept developed in the field of psychobiology and is used to describe the negative impact that ongoing stress has on the body’s systems and processes, including the cardiovascular, immune, and nervous systems.
“Pets are often thought to confer health benefits to their owners, and one of the mechanisms is stress relief. Allostatic load is an ‘objective’ measure of the effect of chronic stress exposure on physiological systems, so our rationale was that pet owners should have lower allostatic load scores than non-owners,” said study author Jennifer W. Applebaum, a doctoral candidate at the University of Florida.
“There is also a robust body of literature on disparities in allostatic load by socioeconomic position (i.e., race, ethnicity, gender, income, education, etc.), so we were also curious if pet ownership may provide enough stress relief to buffer against the harmful effects of chronic stress exposure experienced by marginalized individuals.”
The researchers examined data from the Health and Retirement Study, a longitudinal panel survey of adults aged 50+ in the United States that began in 1992 and collects data every two years. The study continuously enrolls new participants, who are followed until they pass away, with approximately 20,000 people included in each round of data collection.
The main focus of Applebaum’s study was on pet ownership, which was measured using a survey module administered to about 10% of participants in 2012. The study considered different types of pets, including dogs, cats, small mammals, birds, fish, reptiles, and “other.” Physical and biomarker measures were also collected beginning in 2006.
A measure of allostatic load was derived from three physical measures (systolic blood pressure, diastolic blood pressure, waist circumference) and five biomarker measures (hemoglobin A1c, high-density lipoprotein, total cholesterol, cystatin C, and C-reactive protein).
Compared to those who did not own pets, the researchers found that those who reported pet ownership in 2012 tended to have lower allostatic load scores between 2006 and 2016. This relationship remained statistically significant after accounting for wealth and education. However, the effect became non-significant after controlling for race and ethnicity.
“We found some evidence that pet owners had lower allostatic load scores than non-owners, but the effect did not hold statistical significance when we adjusted our models for all of the included indicators of socioeconomic position. In particular, pet ownership lost statistical significance once we put race/ethnicity into the model,” Applebaum told PsyPost.
“This is not that surprising given the very consistent findings across studies related to higher allostatic load scores among, in particular, Black Americans, who are, at the population level, subject to higher chronic stress than Americans of other races. We suspect that the magnitude of the effect of pet ownership on allostatic load is insufficient to counteract experiences of high chronic stress experienced by some marginalized groups.”
The researchers said that pets can have positive effects on health by reducing chronic stress, but that the impact may vary depending on the individual and their social conditions. In some cases, pets may even add to the burden. For instance, while pets may be beneficial in moderately stressful situations, having to care for them might make matters worse in very stressful environments.
“We found that, among those aged 80+, pet owners had HIGHER allostatic load scores than non-owners,” Applebaum explained. “This suggests that pet ownership could actually be stress-provoking for this older age group, but it’s important to remember that the nature of the data and measures didn’t allow us to assess causality, so this is just an association and could be an effect of an unobserved factor. For example, it’s possible that pet owners tend to have characteristics, lifestyles, and or/environments that we were unable to include in the study that are conducive to lower allostatic load than non-owners.”
The new findings are in line with some previous research. For example, a 2022 study found that having a stronger relationship with your dog can actually be related to an increase in anxiety and depression.
But the study, like all research, includes some caveats.
“The nature of the data and measures didn’t allow us to assess causality, so any significant effects could be a result of some unobserved factor,” Applebaum explained. “In order to assess causality in this type of study, researchers would need to collect many more repeated measures about pet ownership and the nature of the pet-owner relationship, as well as control for any other non-pet factors that may impact allostatic load.”
The study, “Longitudinal associations between allostatic load, pet ownership, and socioeconomic position among U.S. adults aged 50+“, was authored by Jennifer W. Applebaum, Shelby E. McDonald, and Barbara A. Zsembik.