Scientists have dismissed the myth that a dog's age is human years times seven. Researchers from the University of California have come up with a new formula to calculate the age of dogs. The study was published in bioRxiv.

The formula is based on methylation, a process where methyl groups are added to the DNA molecule, thereby modifying the DNA segment. In humans, DNA methylation is related to aging, in a process known as epigenetic clock.

Geneticists Tina Wang and Trey Ideker of the University of California compared the epigenetic clock of humans to that of dogs. They studied 104 labrador retrievers up to 16 years of age; previously published methylation data from the blood of 320 humans between one and 103 years old; and methylomes of 133 mice.

"Comparison with human methylomes reveals a nonlinear relationship which translates dog to human years, aligns the timing of major physiological milestones between the two species, and extends to mice," the study said.

The new formula now stands: 16ln(dog_age) + 31

Multiply the natural logarithm of a dog's age by 16 and add 31.

"Conserved changes center on specific developmental gene networks which are sufficient to capture the effects of anti-aging interventions in multiple mammals," the study said.

Researchers have noted that dogs reach puberty and maturity faster than humans due to their faster epigenetic clock. Not only that, factors such as the breed and size of a dog also come into play, hence the varying results. As such, a formula is the best answer to calculating a dog's age.

 "These results establish methylation not only as a diagnostic age readout but as a cross-species translator of physiological aging milestones," the study said.