‘Dog years’ is just a myth: New research shows non-linear relationship between dog and human years

SAN DIEGO, Calif. - “How old is your dog in human years?” That’s a question that most dog owners answer using the “multiply by 7” rule. The adage suggests that a 5-year-old pooch is similar in physiological age to a 35-year-old human. But a new study suggests that the age-old method may actually be a myth.

Researchers at the University of California San Diego School of Medicine found a formula that more accurately measures the age of our furry friends. It turns out that, when looking at the different patterns of methyl groups in dog and human genomes, the two species do not age at the same rate.

The study, published on July 2 in the Cell Systems Journal, found that when dogs are young, they age rapidly compared to humans. A 1-year-old dog is similar to a 30-year-old human, and a 4-year-old dog is similar to a 52-year-old human. Dogs’ rapid aging slows down after they turn 7 years old, according to the study.

Using the novel methylation formula, the researchers found the canine “epigenetic clock,” a method for determining the age of a cell, tissue or organism based on its epigenetics, which are chemical modifications like methylation that can influence which genes turn “on” or “off” without changing the entire gene sequence.

While human epigenetic clocks are not a novel discovery, they were limited to specific individuals and could not translate to other species.

“There are a lot of anti-aging products out there these days — with wildly varying degrees of scientific support,” said senior author Trey Ideker, Ph.D., professor at UC San Diego School of Medicine and Moores Cancer Center. “But how do you know if a product will truly extend your life without waiting 40 years or so?”

“What if you could instead measure your age-associated methylation patterns before, during and after the intervention to see if it’s doing anything?”

Since humans have been a default subject in science, Ideker and his fellow researcher, Tina Wong, Ph.D., decided to study a more interesting and unique species: dogs.

Domesticated dogs are unique in that they live closely to humans more than any other animal, and they therefore have very similar environmental and chemical exposures. They also experience similar levels of health observation and health care intervention as humans.

“Despite extensive phenotype differences, all domestic breeds are members of the same species with a similar developmental, physiological and pathological trajectory as humans,” the report reads.

One limitation that the researchers noted was that they only tested Labrador retrievers. Ideker and his team plan to test other dog breeds to see if their new model for measuring dog years is universally effective and accurate.