- Not a substitute for professional veterinary help.
Most of us grew up believing in the “multiply by seven” rule when determining a dog’s “human” age: basically, one dog year equals seven human years.
But according to a 2020 study published in Cell Systems by researchers at UC San Diego Health, that calculation is an oversimplification.
Trey Ideker, Ph. D., a professor of medicine who led the study, was researching human DNA to understand what changes happen as we age. Tina Wang was his graduate student at the time and had recently rescued a dog of indeterminate age, so she suggested they look at aging in dogs, too.
To do that, the researchers collected blood samples from 105 Labrador Retrievers of all ages to study their DNA. The scientists used “epigenetics,” a complex field of study that essentially looks at the “changes that affect gene activity and expression.”
According to a blog article published by the university, these epigenetic changes “provide scientists with clues to a genome’s age—much like wrinkles on a person’s face provide clues to their age.” This helped the researchers develop a mathematical formula to help determine a dog’s true age, and they found that the old rule of thumb was pretty off.
The article continues: “The comparison is not a 1:7 ratio over time. Especially when dogs are young, they age rapidly compared to humans. A one-year-old dog is similar to a 30-year-old human. A four-year-old dog is similar to a 52-year-old human. Then by seven years old, dog aging slows.”
Pretty neat, right?
Read on to learn how to calculate your dog’s age according to the new data.
How to Calculate Your Dog’s Age in Human Years
Ready for the math? Psychology Today breaks it down below (we tried to figure out a way to explain it ourselves, but couldn’t improve on their expert, albeit slightly confusing, analysis). Here you go.
Wait, What?
Because our love of dogs far eclipses our love of math, we’re just going to leave that there.
The easiest way to explain it is that dogs simply age quickly. As indicated above, a one-year-old dog is around 30 in people years, despite what their rambunctious energy might tell you.
“This makes sense when you think about it—after all, a nine-month-old dog can have puppies, so we already knew that the 1:7 ratio wasn’t an accurate measure of age,” Ideker said.
More Research Is Required Before It Applies to All Dogs
There are limitations to the study, including that it only looked at Labrador Retrievers. Some dog breeds generally live longer than others (such as small breeds compared to large breeds) so the calculation may need to be revised based on breed. Pending further study, Ideker is still hopeful the science behind the formula will still hold up.
The team also hopes that their research will provide a more holistic view of a dog’s age for veterinarians. The American Veterinary Medical Association considers small dogs senior at seven years old and large dogs senior by five or six. It’s unclear whether that stance will change based on the new research, though the association acknowledges the “multiply by seven” model is outdated.
For me, the best news is that my 11-year old dog, who is roughly the size of a Labrador if not a little smaller, got several years of her youth back. According to Ideker’s calculation, she’s just under 70 years old.