New trick to calculate your old dog's age © Getty Images

New trick to calculate your old dog’s age

The researchers say the commonly-held belief that a dog year is equivalent to seven human years is a myth.

Scientists claim to have developed a formula that can compare the ages of dogs and humans more accurately.

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Their work is based on a new concept in ageing research known as epigenetic clock, which analyses the chemical modifications to a person’s or a species’ DNA over a lifetime to determine their age.

According to the researchers, the findings, published in the journal Cell Systems, debunk the traditional method which involves multiplying a dog’s age by seven to calculate how old they are in “human years”.

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To understand more about the ageing process in dogs, the researchers gathered blood samples from 105 Labrador retrievers. They sequenced the genomes, or the genetic material, of the Labradors with the aim to track a process known as DNA methylation, which many species undergo as they age.

Dr Trey Ideker, a professor at the University of California, San Diego, US, and one of the study authors, said these epigenetic changes provide clues to a genome’s age – much like wrinkles on a person’s face provide clues to their age.

He said dogs are interesting to study because they live closely with humans, receive nearly the same levels of health care, and have similar environmental and chemical exposures.

This handsome seven-year-old dog is 62 in human years © Sara Rigby
This handsome seven-year-old dog is 62 in human years © Sara Rigby

They found the canine epigenetic clock to tick much faster than the human one, especially in the initial years.

The way to calculate your dog’s age in human years, say the researchers, is through this formula: age in human years = 16 * ln(age in dog years) + 31, where ‘ln’ means the natural log.

Based on their calculations, the researchers say a one-year-old dog is similar to a 30-year-old human, while a four-year-old dog is equivalent to a 52-year-old human.

Dr Ideker said: “I have a six-year-old dog – she still runs with me, but I’m now realising that she’s not as ‘young’ as I thought she was.”

He said that one of the limitations of their canine clock is that it was developed using only one dog breed, and some breeds live longer than others.

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Dr Ideker plans to test more breeds, but he predicts the clock will apply to all dog breeds because it is “accurate for humans and mice as well as Labrador retrievers”.

The researchers also claim their methylation-based formula could be useful in testing anti-ageing treatments.

Dr Ideker said: “There are a lot of anti-ageing products out there these days – with wildly varying degrees of scientific support. But how do you know if a product will truly extend your life without waiting 40 years or so?

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

What is DNA methylation?

All of our cells contain DNA, which is a series of sequences of bases known as A, G, T and C. DNA methylation is a biochemical process where methyl groups are added to particular sites in the DNA sequence called ‘CPG sites’.

In the genome, there are areas where there are clusters of these CPG sites. The methyl groups get added to these sites and they affect the likelihood that a gene will be expressed. That’s what really matters.

You can inherit a gene from your parents that might have some adverse consequences on your health, but if that gene is not expressed, it doesn’t matter.