A study on a national sample of U.S. adults above 50 years of age found that persons above 65 who owned a pet for more than 5 years had higher cognitive scores and higher immediate and delayed word recall scores (better memory) compared to people of the same age who did not own a pet. There were no differences between pet owners and people who did not own a pet below the age of 65. The study was published in the Journal of Aging and Health.
Dementia is a group of irreversible neurological syndromes associated with cognitive decline and adverse behavioral changes that primarily affects people of advanced age. There are around 5.8 million Americans currently living with dementia. Although the share of older people with dementia has been decreasing in recent years, the total number is expected to rise as the baby boomer population ages.
The risk of dementia increases with age, with only 3% of persons between 70 and 74 years of age having dementia, compared to 22% of those between 85 and 89 and 33% of persons above 90. Women are slightly more likely to have dementia than men.
Education has been found to reduce the likelihood of developing dementia and a number of other factors have been found to have the same effect. These factors include physical inactivity, depression, social isolation, cardiovascular disease, hypertension and chronic stress. Approximately one-third of dementia cases are attributable to modifiable causes such as these and other similar lifestyle related factors.
Pet ownership is one aspect of lifestyle that is known to influence many health and disease outcomes via emotional support and stress buffering. “Many older adults are pet owners, yet little is known about the potential cognitive effects of pet ownership in older age; namely, whether pet ownership could be protective against cognitive decline,” said study author Tiffany J. Braley, an associate professor of neurology at University of Michigan.
To evaluate the associations between ownership of a pet and measures of cognitive health among older U.S. adults, the researchers analyzed data from the Health and Retirement study, “a large, nationally representative and diverse prospective cohort of US adults aged 50+, designed to investigate the health, social, and economic implications of aging of the American population.”
Organized by the University of Michigan, this study surveys a group of 20,000 participants every two years, since 2010. Questions about companion animals were included in the study in 2012 and this paper analyzed data from surveys done between 2012 and 2016.
In the survey, participants were asked about pet ownership, including “Do you currently have any pets?” and “How long have you had your (pet/pets)?”
The study assessed cognitive function with a variety of objective tests. The researchers explained that these results were used to create a total cognitive assessment score, but also to classify participants into those with normal cognition, those with a cognitive impairment, and those with dementia. This study analyzed only data from participants who had normal cognition in 2010.
Results showed that 47% of participants reported owning a pet in 2012. At that time point, 19% owned a pet for between 1 and 5 years and 28% for more than 5 years.
“We found that, among those aged 65+, long-term pet owners (>5 years) demonstrated better cognitive performance than those who owned pets for shorter periods of time, and those who did not own pets at all,” said study author Jennifer W. Applebaum, a doctoral candidate at the University of Florida. “We conclude that long-term pet ownership may impart some protective effects against cognitive decline, but further research is needed to both confirm the findings and to understand how and why this may be the case.”
The association between owning a pet and cognitive performance was the strongest for verbal memory. “Sustained pet ownership was associated with higher immediate and delayed word recall scores,” the researchers wrote.
However, differences in cognitive scores were not found between these groups when participants below 65 were considered. The study also found that those who owned a pet for a period above five years showed indicators of greater physical activity, lower body mass index and lower incidence of diabetes and hypertension compared to participants who owned a pet for a shorter period or did not own one.
“Sustained ownership of a pet could mitigate cognitive disparities in older adults,” the researchers wrote.
“I was surprised that the findings held up with rigorous statistical controls,” Applebaum noted. “We adjusted the statistical models for sociodemographic factors, which allowed us to account, at least in part, for the effects of known health disparities (e.g., race, socioeconomic status). Oftentimes, any positive health effect of pet ownership disappears in statistical models when accounting for health disparities, likely because the health effects of social inequalities are so profound.”
The study contributes to our knowledge on pet owners of advanced age. However, it should be taken into account that it does not allow for cause-and-effect conclusions. Notably, it is possible that observed differences come from the fact that people in better mental and cognitive condition are more able to take care of a pet and are thus able to keep one and not necessarily that pet ownership reduces the rate of cognitive decline.
“While the longitudinal associations in our study are compelling, the design of the study did not allow us to demonstrate a cause-and-effect relationship,” Braley explained. “Additional prospective work that includes information on strength of the human-animal bond and its effect on cognitive trajectories, and incorporates study of biological mechanisms that could mediate this relationship, are still needed.”
The study, “The Impact of Sustained Ownership of a Pet on Cognitive Health: A Population-Based Study”, was authored by Jennifer W. Applebaum, Monica M. Shieu, Shelby E. McDonald, Galit Levi Dunietz, and Tiffany J. Braley.
