Ricky Bobby, Elwood, Lexi Lemon, Ginger, Max, Sully, Ziggy, Zelda, and Pop Tart - each of these dogs has its own story, gait and personality. But they're more than just pets. They're integral to a five-year research project aimed at deepening our understanding of chronic pain in dogs that live alongside us, sleep on our couches, and grow older with us.
For decades, pain research has relied heavily on rodent models. But an initiative by the National Institutes of Health to reduce reliance on opioids by humans is pushing scientists toward non-rodent models that better reflect human chronic pain.
It's called the Helping to End Addiction Long-term Initiative (HEAL), and Duke University's Canine Cognition Center and NC State are collaborating. NC State conducts medical workups and assessments of emotional state, while the Cognition Center focuses on testing memory, problem-solving, and self-control.
The goal is to come up with models to measure pain and to develop ways to treat that pain in both dogs and humans without relying on opioids.
How Dogs Deal With Pain
"In humans, we know that pain really impacts your memory, your self‑control, your social relationships," says research scientist Vanessa Woods, who coordinates the Duke portion of the HEAL project. "We're looking at the whole cognitive battery (and) trying to narrow it down to establish what cognitive tests would be affected by a dog who's experiencing pain, particularly a dog with osteoarthritis."
Dr. Margaret Gruen a veterinary behaviorist at NC State's College of Veterinary Medicine, recognized an opportunity for the two universities to collaborate, which led to a $5.5 million grant from the NIH nearly two years ago.
The study has screened 163 dogs, of which 45 are enrolled. Twenty-two have osteoarthritis, and the rest are healthy controls. Screening is rigorous: dogs must show owner-reported signs of pain, pain on orthopedic exam, and radiographic evidence of the disease.
The dogs go through a series of tests focusing on problem-solving and spatial reasoning skills. They are designed to measure cognition, emotion and enjoyment of life. The idea being that dogs, like people, perform differently when dealing with pain.
"Rodent models have gotten us very far, but there are some areas they're missing," Gruen says. Dogs offer something rodents can't: naturally occurring osteoarthritis that often develops earlier in life and progresses in ways like those in humans.
"Dogs live in our environments, eating the same types of food we do, breathing the same air, and exposed to the same potential risk factors," Gruen explains. "So, they are a great model for us here, and the work helps the dogs, too."
The testing is all voluntary. The dogs must want to participate: "We wanted to make sure that we were separating the cognitive testing (from medical testing) and the expertise at Duke makes the Canine Cognition Center an ideal option for that," said Gruen, who has previously worked with Cognition Center on other studies and who did her postdoctoral education there.
This separation matters. As Duke undergraduate researcher Katarina Feetham explains, "Dogs that may have a fear of the vet or get antsy around medical places can do the cognitive testing removed from their medical testing… so that separating the testing can remove that confounding variable."
Lab coordinator Alyssa Pulido , who runs many of the tests, sees the differences firsthand. "You can tell when those osteoarthritis dogs are like, I'm tired and I'm hurting and I don't want to keep going," she says. In one test, dogs must walk increasing distances to reach a bowl. "They just don't want to walk anymore because it hurts."
The cognitive and emotional angles make this study groundbreaking. In humans, chronic pain affects memory, attention, impulse control and social behavior. However, these effects have rarely been studied in animals.
If successful, the team hopes that veterinarians could one day use a simplified version of these tests to measure the impacts of pain on emotional state and cognitive function.
Woods sees the work as a bridge between species. "Dogs are actually a much better model for people in many ways," she said. "The overlap between human and canine diseases is super fascinating.
The NIH grant encouraged adding a human clinical team member to provide input on the human pain experience. That's where Dr. Francis Keefe came in. Keefe leads the Duke Pain Prevention and Treatment Research Program.
The Human Pain Perspective
Keefe said he is intrigued by how dogs could help reveal the social aspects of pain, a complex area to study in humans.
"Dogs may provide a better model for understanding pain mechanisms and developing new treatments than rodents," he says.
He's particularly interested in how owners influence their dog's pain experience. "An owner who encourages a dog in pain to remain active may positively influence both the disease process and the dog's functioning," he notes. Conversely, overly protective behavior can worsen outcomes. This pattern is also seen in humans.
Keefe views the project as an opportunity to reshape research. "If the model works as anticipated, it could become a very promising research platform (and) significantly advance our understanding of pain and improve translation to humans."
The team is still in the data collection phase, but early results indicate the tests are stable, with dogs performing similarly at weeks zero and four. This is crucial before the project is scaled up.
The next phase would include 250 dogs, tested repeatedly, with some receiving pain treatments and others placebos. The goal is to determine whether cognitive and emotional markers improve as pain improves.
"Dogs are even more important to us once they've lived a full life and been part of our families for such a long time," Woods says. "I just love being involved in research that helps us take care of them and repays them for some of that unconditional love."
