1 dog year equals 7 human years? Researchers think this is wrong!
New York - The widespread rule of thumb regarding the age of dogs, according to which one year is roughly equivalent to seven human years, is considered by US researchers to be quite wrong.
According to genetic analyses, the four-legged friends do not age at a consistently faster rate than their masters, write Trey Ideker from the University of California San Diego and his team in the scientific journal "Cell Systems". Instead, young dogs age particularly quickly compared to humans, but later on the ageing process slows down.
Instead of the simple 7-year rule of thumb, the researchers propose a somewhat more complicated formula based on their studies on 104 Labrador retrievers: "Human age = 16 ln(dog age) + 31". This is a so-called logarithmic function. If you want to calculate with the formula yourself, you should have a calculator at hand that has the "ln" (natural logarithm) key.
According to this, a one-year-old dog would not be comparable in age to a seven-year-old human, but to a 31-year-old human, and a four-year-old dog to a 53-year-old human.
At nine, a dog would then have reached the comparable human age of 66 years.
How did the researchers come to this conclusion?
In their analysis, the researchers focused on tiny changes in the DNA. These numerous DNA methylations occur in both humans and dogs. The methylations form certain patterns in the genetic material that indicate the life phase of an individual.
The researchers took advantage of this and established a connection between the age-dependent patterns in dogs and those in humans. They derived the new formula from their findings.
It is important to better understand the ageing process of dogs, said Ideker according to a press release from his university. Veterinarians often still use the old 7-year rule of thumb and make diagnostic and therapeutic decisions based on this.
However, further studies are needed, the researchers write. The new formula was only developed on the basis of the Labrador retrievers studied. The formula could differ for other dog breeds that have a lower or higher life expectancy.
He now sees his own dog with different eyes, said Ideker. "I have a six-year-old dog. She still goes jogging with me, but I now realize that maybe she's not quite as young as I thought."