Pets can bring a lot of joy to their households, along with tangible social, emotional, and physical health benefits for their owners. It is thought that interacting with or sharing a household with animals could have a range of benefits like providing companionship, providing and facilitating social interactions, reducing loneliness and stress, increasing physical activity, improving sleep quality, reducing blood pressure and heart rate, or even influencing immune system function. Mitigating or preventing cognitive decline may be another benefit of pet ownership.
WHAT THE EVIDENCE SAYS
Several studies have examined the relationship between pet ownership and cognitive health. One study looked at data from almost 8,000 adults in the English Longitudinal Study of Ageing [1]. They found that pet owners typically had slower rates of decline in some areas of cognitive function, like verbal cognition, verbal memory, and verbal fluency. Pet ownership was associated with slower cognitive decline for individuals who lived alone, but not in those who lived with other people. Living alone later in life is a risk factor for dementia - on the scale of other risk factors like diabetes, hypertension, obesity, and hypertension [2; 3]. While it is often not easy to change your living arrangement, pet ownership may offer a more accessible route to some of the same benefits.
A study of 378 participants in the Baltimore Longitudinal Study of Aging found that after controlling for age, pet ownership overall was associated with better cognitive function as measured by verbal learning / memory. Dog ownership was associated with better physical function, and both dog and cat ownership were associated with better cognitive function [4]. A larger 637 person follow-up study from the same cohort found that after controlling for age and pre-existing health conditions, pet owners had had significantly less decline of cognitive functions like memory, executive function, language use, and processing speed. These differences were seen for both dog and cat owners. When looking only at dog owners, the researchers found that people who walked their dogs had less cognitive decline as compared to those who did not walk their dogs [5]. Another study of 95 adults aged 20 to 74 found that pet owners, particularly those with dogs and/or multiple pets, tended to have better cognitive scores in certain domains. They also found that pet owners had larger brain volumes in key areas related to these cognitive domains, and that the brains of pet owners looked younger based on brain structure measured by imaging (MRI) than non-pet owners [6].
All of the above studies are observational studies, meaning researchers collected information about people’s lives and looked at whether certain lifestyle factors were statistically related to their cognitive function. These types of studies are not designed to prove cause versus effect. For example, healthier people with good baseline cognitive function may be more likely to have pets – and those factors could be what is driving the differences in cognitive function rather than the pet themselves. Randomized controlled trials are the gold standard in determining whether an intervention or treatment is effective. Although there are ethical reasons why randomized controlled trials cannot be performed with pets such as cats or dogs, a small randomized controlled trial of 94 participants reported that participants who were assigned to take care of 5 crickets for 8 weeks had significant improvements in cognition and measures of depression compared to a control group that received education about healthy lifestyle choices [7]. Insect pets of course are not the same as dogs or cats, but they do require care and attention.
It should be noted that not all studies find the same positive associations of pet ownership. Some studies have not found meaningful differences in cognitive function or other markers of health between those who have pets and those who do not [8; 9; 10].
REMAINING QUESTIONS
How pet ownership could provide cognitive benefit is an open question. According to the American Heart Association, pet ownership – particularly dog ownership – is probably associated with decreased risk of cardiovascular disease [9]. Reducing cardiovascular risks can reduce risk of cognitive decline. Pet ownership, particularly dog ownership, may also lead to increased duration or frequency of physical activity, and exercise can also in and of itself be beneficial for cognitive health. Besides for exercise, walking your dog may result in more meaningful interaction with green spaces or otherwise increase benefits of being outdoors. Pets can reduce loneliness, both directly and through facilitating interactions with other people, such as through making friends at the dog park. Having a pet can also potentially lead to cognitive benefits more directly. For instance, taking care of an animal requires several complex cognitive tasks such as paying attention to the animal and their surroundings, planning and remembering to complete tasks, and emotional regulation. Practicing these skills regularly could lead to improvements in brain health. These benefits are also not mutually exclusive, so there may be indirect and direct benefits.
More research is needed, though, to confirm whether pet ownership truly has cognitive benefits. It is challenging to rule out confounding factors – for instance, that healthier or wealthier people or people from particular groups are more likely to have pets, and that pet ownership is a correlation rather than causation. The details of pet ownership also remain to be teased apart. Does the kind of animal matter? How long do you need to have a pet to see benefit? Are the benefits lasting, or only so long as you share a household with the pet? Does your feeling of attachment to the pet or your level of caregiving responsibility affect the level of benefit you experience?
WHAT YOU CAN DO
The decision to become responsible for the health and welfare of another living being for the rest of their life should be made carefully and thoughtfully. As the American Heart Association states, bringing an animal into your home should not be done for the primary purpose of reducing your disease risk [9]. Many factors go into the decision of whether to have a pet, such as your living situation, your physical abilities, your financial resources, and your lifestyle preferences. If having a pet is right for you, deciding what type and breed of pet to have is an important choice. You and any future pet are best served by finding a pet that is best suited to you- even if that is having no pet at all. For those for whom pet ownership is not the right choice but who would enjoy interacting more with animals, other activities such as fostering, volunteering at a local animal shelter, or pet sitting for neighbors might be worth exploring. Many studies find that animal interactions overall can provide benefits in terms of physical, mental, and cognitive health [4; 10]. Your local humane society or veterinarian is a good resource to help figure out whether a pet is a good fit for you.
Kathryn Carnazza, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Carnazza earned a doctorate in neuroscience at Weill Cornell Graduate School of Medical Sciences, where she studied the molecular mechanisms of Parkinson’s disease. She also founded and organized a graduate school course on neurodegeneration at Weill Cornell. Dr. Carnazza obtained her bachelor's degree in biology from Tufts University.
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