Dogs Get Dementia Too, Say Scientists — Here Are the Red Flags To Watch for in Your Senior Pet

Dementia is a devastating condition that is, unfortunately, not limited to humans. Some pet dogs hit old age and become horribly confused, losing their house training and the ability to recognize their loving owners. “Other dogs are seemingly sharp as a tack until the day they go,” says dog-cognition expert Evan MacLean, PhD, at the University of Arizona.

Why some dogs remain cognitively quick-witted while others experience steep declines is a scientific puzzle. It’s “something we know next to nothing about,” says MacLean, who is part of a team of US scientists undertaking an ambitious study on aging in a very large dog pack. Living not in a lab but with their humans, surrounded by the creature comforts of home, the canine participants in the Dog Aging Project, headquartered at the University of Washington, could help usher in a whole new understanding of aging across all species, including our own.

Dogs Have Long Aided in Laboratory Studies

Dogs have long aided science in laboratory studies. Frederick Banting, Charles Best and their colleagues discovered the hormone insulin with laboratory study of diabetic dogs. In a lab setting, scientists can control the environment. And in short-lived species like mice and rats, we can do experiments in a short amount of time.

But the study of human aging is complex, says University of Washington longevity expert Matt Kaeberlein, PhD, co-director of the Dog Aging Project with his colleague Daniel Promislow, PhD. Humans age much more slowly than laboratory animals and their environment is complicated, says Promislow. Bridging the gap between long-lived humans and short-lived mice, and especially ideas for probing the mysteries of aging, are our pet dogs.

They live shorter lives than humans, aging “about seven to 10 times more rapidly than people do,” says Kaeberlein. It’s a time frame that allows findings to be applied. Plus, our pets share our environment. “They share everything with us,” says recently retired director of the National Institute of Aging, Felipe Sierra, PhD. Because of that shared environment, “they are really the best model,” he says.

So many of the dogs now contributing to science don’t live in sterile lab cages. They are not inbred strains that all get their rodent chow on a 12:12 light:dark cycle. In their human homes, they experience air pollution. They have differing amounts of exercise, diverse feeding times, and dietary regimens. Some have health care comorbidities. “All kinds of things make them much more aligned with our lives as humans than traditional animal models,” says MacLean. As companion animals living alongside us, dogs make it possible for scientists to closely examine environmental variables to see which ones contribute to cognitive dysfunction or resilience in old age.

“I’ve always had dogs my entire life… it’s been a constant since I was a little kid,” says Kaeberlein, who is the owner of a beloved nine-year-old German shepherd. His involvement in the project was an opportunity to combine two passions: human aging research, and life with dogs.

Dogs and Dementia

As dogs hit their senior years — at about 8 years old for a large animal and 11 for a smaller one — cognitive decline and the onset of dementia are a possibility. When it comes to age-related cognitive disorders in humans, “Alzheimer’s is really the big one. It’s obviously devastating for so many people,” says MacLean, who was invited into the Dog Aging Project for his cognition expertise. There are not many good natural models for Alzheimer’s but “dogs happen to be one,” he says. In order to study cognitive decline in rodents, genes need to be tinkered with to create transgenic mice that develop dementia-like pathologies with age. Dogs, in contrast, spontaneously develop much of that pathology. “You don’t have to induce it,” MacLean says. With age, dog neurons develop plaques and get tangled up in ways that limit the brain’s ability to communicate. “It’s obviously sad that some old dogs suffer dementia and this neuropathology, but it makes it really powerful as a learning tool because it occurs naturally,” he explains.

What determines whether a dog develops cognitive impairments or not? Are certain dog breeds more susceptible to impairments than others? Are there lifestyle factors that predict these kinds of impairments? These are some of the doggone intriguing questions the Dog Aging Project hopes to answer as it proceeds from data collection to analysis and discovery.

Healthy Aging for Pooches

Simple lifestyle changes in diet, exercise, and mental engagement will extend and enhance life for dogs.

• Yes, you can teach an old dog a new trick — and doing so is good mental stimulation for their aging brains. “The ability to learn new things seems relatively well-preserved in old dogs,” says dog-cognition expert Evan MacLean, PhD.
• As in humans, the impairments that dogs develop with age are specific. Certain impairments may impact quality of life, but others will not prevent your dog from living life to the fullest. So “don’t give up,” says MacLean.
• For life span, body size is the biggest factor. Big dogs die earlier, often before their brains are affected by dementia. Small dogs typically live longer, putting them at increased dementia risk.
• Healthy aging in dogs, like in humans, may be aided by a healthy diet, and not overfeeding. Data is still being gathered, but “we expect that obesity and diabetes will be associated with faster aging in dogs,” says longevity expert Matt Kaeberlein, PhD.
• Regular exercise slows down aging, so get out for a dog walk and playtime.
• Keep dogs away from air pollution. Just as in humans, it’s linked to faster aging. (The Aging Dog Project will be looking at its impact by ZIP code.)

By the Breed

Nearly 20,000 dogs from all breeds across the United States are currently enrolled in the Dog Aging Project, which launched in 2018. Participant numbers continue to grow. In the study, general characteristics of dogs’ lives are explored with an annual survey that asks detailed questions about age, physical activity levels, environment, behavior, diet, medication, health status, and owner traits. This data reveals things like whether dogs are trained athletes or couch potatoes, or city slickers versus urban dwellers. Dog-cognitive function is also assessed through owner-led surveys. Such surveys, combined with behavioral assessments, are useful tools in veterinary medicine to diagnose canine cognitive decline.

MacLean’s previous research in another project called Dognition provides some preliminary clues about how dog brains age. One discovery he contributed to was understanding the influence of dog breed. Surprisingly, the pace of aging didn’t vary much at all, “which is wild,” says MacLean. A Great Dane might live to be 7 years old and a Chihuahua might live to be 18. So their working hypothesis was that cognitive impairments would scale and “kick in when you reach 80 percent of your expected life span or something,” he says. But they found no evidence for that. Big dogs, with their shorter lives, most often die before they suffer major impairments. Small dogs, in contrast, may live for years in a relatively impaired state.

While there are currently no pharmaceutical interventions that slow the effects of aging, the Dog Aging Project includes a clinical trial on the drug rapamycin, which has already shown promise in laboratory rodents as potentially preventing and reversing Alzheimer’s disease; its influence on dogs will be fascinating to see. Another part of the project will sequence the genomes of exceptionally long-lived dogs to mine their genetic secrets. And for 1,000 selected dogs for which medical records are available, researchers will look for molecular markers of age.

Hints about cognitive aging have also emanated from the Clever Dog Lab at the Messerli Research Institute in Vienna, Austria. There, veterinarian and animal behavior expert Durga Chapagain, PhD, led a study that focused on pet dogs of multiple breeds, developing a series of behavioral tests to study attention, learning, and memory. Just like in humans, one of the age-defying secrets her research revealed was the protective benefits of lifelong cognitive engagement and learning.

Understanding how cognition changes with age in dogs is important in multiple ways, says Chapagain. Beyond benefiting humans and their pets, it has repercussions for working dogs, too. When are assistive and service dogs too old or cognitively impaired to continue work? Right now, there is no clear cutoff. There “doesn’t have to be a subjective way to decide,” she says. Retirement age for dogs, she suggests, could be determined by a scientifically valid test.

The science of dog cognition continues to expand, but already has some answers. Can you actually teach an old dog a new trick? The answer, says MacLean “is a definitive yes.” As for what new tricks humans can learn from old dogs, the Dog Aging Project is just getting started. But there are hints that the lifestyle factors that slow age-related cognitive decline in people — healthy eating, exercise, and mental stimulation — aid resilient cognitive aging in dogs, too.

When it comes to our dogs, “anything we can do to keep them engaged and thinking about the world around them,” according to MacLean, “is probably going to have salubrious effects.”

Looking for Signs

Like humans, senior dogs can get disoriented and irritable when they age. Signs of dementia to look for in your senior dog include:

• Staring blankly, or being unaware of a familiar environment
• Pacing aimlessly
• Appearing to be lost
• Bathroom accidents in bed or in the house
• Not acknowledging or responding to people he knows
• Barking or whining for no reason

A version of this article appeared in our partner magazine, Inside Your Dog’s Mind, in 2021.