Trying to figure out your dog's age relative to human years? Multiplying by seven isn't accurate, a new study says.
Researchers at the University of California, San Diego School of Medicine and other leading health institutions across the country have debunked that common belief. Some say the seven-year myth began circulating decades ago, maybe even earlier, but its origin is largely a mystery.
The real equation is a little more complicated, according to the peer-reviewed study published July 2 in Cell Systems.
And the results show that when dogs are young, especially within their first 5 years, they age even more rapidly than humans.
“This makes sense when you think about it – after all, a 9-month-old dog can have puppies, so we already knew that the 1:7 ratio wasn’t an accurate measure of age,” said senior co-author Trey Ideker in a UC San Diego news release.
Ideker and his colleagues studied 104 Labrador retrievers, spanning a 16 (human) year age range.
According to their findings, a 1-year-old dog is similar to a 31-year-old human.
But still, the rate of aging for any mammal isn't something that can be a perfectly linear comparison to that of humans. The study also found that, after key developing years in dogs, aging drastically slows. A 5-year-old dog, for example, is like a 57-year-old human. And a 10-year-old dog is closer to a 68-year-old human.
The report's presented equation to use is:
human age = 16 ln(dog age) + 31
For iPhone calculators, first input the dog's age. Then click the natural logarithm (or ln) function. Multiply that result by 16. Then add 31.
For Google calculators, first click "ln." Then input the dog's age. Multiply the result by 16, and add 31.
The researchers based the formula on chemical changes in canine and human genomes. Specially, methylation marks – chemical marks on DNA that change with age. It therefore provides a new “epigenetic clock,” or method for determining how old cells are.
As written in the UC San Diego release, the discovery of this equation is more than a "parlor trick" – or just a correction of the ancient, and misguided, 1:7 rule of thumb for assuming the maturity of a family pup.
The methylation-based formula is the first that's "transferable across species."
The researchers say it may provide a useful tool for veterinarians, and for evaluating anti-aging interventions.
Follow the reporter on Twitter @wyatte_gp.
This article originally appeared on USA TODAY: What is your dog's real age? Don't multiply by seven, new study says