Dogs’ risk of dementia increases by half every year

Is your old but beloved family dog suddenly having accidents in the house or getting lost in corners? Has it seemed like your pet sometimes doesn’t recognize someone they’ve known all their life?

Memory loss and cognitive decline are common enough for aging dogs, just as they are for humans. But in extreme cases, scientists say, dogs can experience something called canine cognitive dysfunction, or CCD for short. Other symptoms can include disrupted sleeping patterns, loss of spatial awareness, and new and unusual social behaviors.

“Dogs experience many of the same age-related diseases that we do,” says Sarah Yarborough, an epidemiologist at the University of Washington Department of Family Medicine, in an email.

“Gaining a better understanding of how these diseases manifest in our dog population may give us clues that will better explain the disease progression of [human] diseases like dementia,” she says.

To dive more deeply into risk factors associated with CCD, Yarborough and her colleagues recently collected data from more than 15,000 owners about their pooches, and then adjusted that information to account for variables such as age, breed, and activity level. After all, dogs as a species—Canis familiaris—include everything from the teacup Chihuahua to the Great Dane, and those differences in size, shape, and demeanor could skew the findings. (Here’s why chocolate labs don’t live as long as other retrievers.)

In the end, the scientists learned that the odds of CCD went up by more than half for each year of a dog’s life.

“When two dogs have the same sterilization status, health problems, breed type, and activity level, the risk of CCD is 52 percent higher in the dog who is one year older than the one who is one year younger,” says Yarborough, who is also the lead author of a study published today in Scientific Reports. 

What’s more, dogs described as inactive by their owners were nearly 6.5 times more likely to suffer from CCD—though the experts stress that this link was a correlation, not causation. In other words, they can’t say for sure that inactivity led to CCD or if developing CCD triggered the inactivity. That will require more research to untangle, Yarborough says.

The Dog Aging Project

Earlier studies have found a connection between aging and CCD, but they’ve tended to be much smaller in scope.

In the field of veterinary medicine, a study of a hundred dogs is often looked at as impressively large, says Natasha Olby, a clinician scientist and veterinarian at North Carolina State University, who was not involved in the new study.

This recent study, however, uses data from a groundbreaking 15,000 dogs. It’s possible because of the Dog Aging Project. Founded in 2014 by Kate Creevy, Daniel Promislow, and Matt Kaeberlein, and funded in part by grants from the National Institute on Aging, the novel project collects information about tens of thousands of dogs across the United States as they grow. In some cases, owners also supply veterinary records and biological samples, such as genetic material.

While Olby’s laboratory takes the opposite approach to study aging—individual dogs are evaluated by multiple specialists—everyone is seeking answers to the same questions, she says. (Learn why dementia is more unlikely in wild animals.)

“The beauty of this is that we can validate hands-on observations coming in from people via questionnaires,” she says. “We are finding great synergy between our groups.”

Helping dogs, helping people

The good news for both dogs and dog owners is that CCD is relatively rare. Just 1.4 percent of the dogs in the study showed signs of the disease. The catch is, that statistic refers to dogs of all ages. At a certain point, cognitive decline becomes inevitable, it seems.

“We find once they get up to 15, we have yet to see a dog that is normal,” Olby says.

There also may be more dogs out there with CCD than were reflected by the study. 

“I have to say, I don’t treat a lot of dogs with cognitive dysfunction,” says Andrea Y. Tu, medical director of Behavior Vets of New York, who was also not part of the new research.  

This may be because many pet owners simply view dementia as a normal sign of aging. And if a dog isn’t causing a problem, like biting people, owners don’t seek treatment, she says.

The condition can also be difficult to diagnose based on a single symptom. As an example, when a dog starts having accidents in the house, it could be the result of a bladder infection, not dementia, Olby says. Similarly, brain tumors can also induce dementia-like symptoms.

Simply being aware of CCD, however, might help pet owners recognize it sooner and slow its progression.

“In people, there’s so much evidence that keeping mobile and doing exercise will help delay dementia, and maybe even reverse it a bit in the early phases,” Olby says.

Likewise, when a dog begins to show signs of slowing down, a pet owner might ask their veterinarian if there’s anything that can be done. For instance, Olby says, anti-inflammatory drugs could help ease arthritis-related pain, allowing an old dog to stay active for longer and potentially staving off cognitive decline.

There may be benefits for aging people, too.

“I certainly do believe that canine cognitive dysfunction can be a model for human Alzheimer studies,” says Tu, who went on to say that imaging the brains of dogs with CCD would allow scientists to draw even more conclusions from the Dog Aging Project data.

Another reason dogs are especially interesting model animals for these sorts of studies, Olby says, is because they get these types of age-related diseases naturally, rather than via scientists inducing them artificially in a lab.

“They also live with their owners, in the same environment, often eating the same foods, on the same bed, or exercising at the same time,” Olby says, “so we have a really unique way to understand these often very subtle, cumulative environmental cues much better by looking at the dogs. I get quite excited at the potential.”