Most dog owners have dealt with the sadness of watching their beloved companion age at what seems like an unreasonable pace. The Labrador who’s so energetic and puppy-like at four is slow and gray at nine, and dead at 11.
To biologist Daniel Promislow, the dog aging process is not only distressing, it also doesn’t seem to make sense. In most of the animal kingdom, larger animals live longer than smaller ones. Humans outlive chimpanzees. Tigers outlive house cats. Orcas outlive dolphins. But within the dog species, the opposite effect is true. A five-pound Chihuahua can live up to 18 years. A 150-pound Newfoundland lives about 10.
“There’s no such thing as a 15-year-old Great Dane,” Promislow says.
Promislow, who has worked on the biology of aging for most of his career, began to wonder about just how aging worked in dogs. What were the biological and environmental factors that effected life span? Could lifespan be modified?
His questioning has turned into the Dog Aging Project at the University of Washington, where he works. The project is currently engaged in research on understanding dog aging and using medications to potentially enhance life span. The team is also currently being reviewed for a grant that would allow them to conduct an enormous longitudinal study on dog aging involving some 10,000 dogs from across America.
“Dogs are the most phenotypically variable species in the world,” Promislow says. “You just go to the dog park, and you see that variability in terms of size, shape, color, coat and behavior. They vary not only in those things we can see, but also in their life span.”
Promislow and his team are currently recruiting dogs of all kinds—large and small, purebreds and mixed breeds, young and old. They’re also interested in dogs from geographically diverse parts of the country and from households of different socioeconomic backgrounds.
“We’ll determine genotype of every dog, measure epigenome, microbiome, metabolome, and we’ll try and put together measures for aging for the dogs that we don’t have,” Promislow says.
There are several easy metrics for measuring aging in humans, Promislow says. You can, for example, measure frailty—a condition in older adults involving loss of strength and speed, and a risk factor for many poor outcomes—by seeing how quickly a person can get out of a chair. But there’s no such chair test for dogs, which makes it hard to evaluate how well or poorly a dog is aging.
Understanding dog aging may have benefits for humans as well.
“Because dogs live in our environment, there’s potential for them to be sentinels for environmental risk factors—air quality, water quality, things about the home,” Promislow says. “These are immediately candidates for risk factors that might be affecting life span in people.”
The project is also testing whether a compound called Rapamycin can help dogs age better by protecting their cardiovascular health. The team has run a phase-one clinical trial on 25 dogs, putting a third of them on a high dose of Rapamycin, a third on a low dose, and a third on a placebo. Both the low and high dose groups appeared to show improvement on heart function, Promislow says, though the data has not yet been submitted for peer review.
If the current grant request is funded, the team hopes to enroll many more dogs in a Rapamycin trial.
Promislow and his team also envision the study as a way of getting people, especially students, interested in science. They plan to make much of their data publicly available, so anyone can ask their own questions and do their own analysis.
“[The project] captures the imagination of people who are dog owners and who have watched their dogs age quickly, but it also has the capacity to really improve our own feelings about science and what science can do,” Promislow says.
Promislow himself is the owner of an 11-year-old mutt who’s so vigorous people think she’s a puppy. Last year, his purebred Weimaraner died at 11, already fairly feeble and aged. This is one of the questions Promislow hopes to investigate—how does inbreeding affect life span, and does outbreeding (mixing two purebreds to make a non-purebred) enhance life span?
Promislow and his team are counting on America’s love of dogs (they’re the most common pet in the country, with more than a third of American households owning a dog) to help them recruit pets for the study.
“People are really close with these animals, and it’s very hard to watch them aging,” he says. “Seventy percent of pet owners consider the dog a member of the family. That’s partly what excites people about this project.”