Scientists have developed a more accurate way to determine dogs' ages, rather than multiplying human years by seven.
Researchers from the University of California, San Diego, looked at changes in canine DNA over time and found that certain chemical tags follow a predictable pattern with aging. They then compared these markers with human DNA and created a new formula for determining dog years.
"They age really rapidly as puppies compared to older canine adults," said Dr. Trey Ideker, professor of Genetics in the Department of Medicine at UC San Diego and lead investigator of the study.
"If you think about it, the one dog year to seven human years thing already didn't make much sense," Ideker said, "a nine-month-old Labrador retriever can have puppies . . . So you see in our model that those 9-month-old labs are actually like 25-year-old women."
The chemical tags that the scientists studied are added to DNA with aging. This age-related change is called methylation and occurs in every species, including humans.
"Now that we have a molecular understanding, we're one step closer to understanding aging," Ideker said. "We get wrinkles as we get old but what's really the root? [It's] molecular."
Because these canines live so closely with humans, they encounter many of the same environmental exposures that humans do and about the same health care use. Given these similarities, Ideker said, "Dogs are just a fantastic model for healthy aging."
All this information provides new insights into human aging. Ideker shared that this research "pinpoints where those aging genes might be, because we can see where the changes are happening . . . and they are particularly in genes related to development. So, it's really going to help the aging field understand more about aging and how it happens."
Not only do these findings provide insight into the molecular basis of aging, but they may help with future interventions to slow aging. Ideker is most interested in "How can we help in a preventative way for humans to monitor how fast they're aging and maybe correct that?"
So the next time you are playing fetch with your furry friend, go easy on him, because he might be a bit more up in years than you think.
Stephanie E. Farber, MD is a plastic surgeon from Pittsburgh, Pennsylvania, and is a contributor to the ABC News Medical Unit.