WHAT AGE IS CONSIDERED OLD FOR A DOG?

By Dr. Monica Tarantino DVM


We’ve all heard the old adage that says for every human year a dog ages 7 years. But what does that mean for your dog? In today's blog, we'll dive into what one recent University of California study suggests about how your dog ages.


At the most basic level, the old' 7 years for every human year' adage tells us that our dogs age faster than us. But in my opinion, that's really all the adage does for us. For those interested in a simple aging chart that I have created, you can download one here.


For the rest of you, let's discuss what the latest data is showing!


Based on a study done out of University of California San Diego (UCSD), dog aging is a bit more complicated than we thought! And if you are using the old adage mentioned above to estimate your dog's age, you may actually be underestimating their age based off of this recent look at their DNA. Let's look closer at this study a bit.


In July 2020, UCSD (my alma mater!) researchers performed a study where they looked at DNA of 104 Labrador Retrievers. They specifically looked at the methyl groups on this DNA and compared it to the amount of methyl groups that humans accumulate as they age. As humans (and mammals) age, their DNA starts accumulating methyl groups. For people, the amount of methyl groups that we accumulate on our DNA correlates well to our age (Ex: a 50 year old has more methyl groups then a 25 year old which has more methyl groups than a 15 year old and so on).


Scientists can actually determine the age of a person fairly accurately based on how many methyl groups their DNA accumulates.

So researchers at UCSD, decided to look at how dog’s accumulate methyl groups onto their DNA and compared them to physiological milestones (puberty, etc.). And the findings were far different than what one might think!


Just like most mammals, dogs accumulate methyl groups as they get older, only they do NOT do it in a linear fashion like humans. This study showed that the DNA of dogs ages A LOT faster right in the beginning of their lives.

The data from the study suggests that the amount of methylation in a 1 year old lab correlated to that in a 30 year old human.

Then later in a dog’s life, they accumulate methyl groups as a much slower rate. And so the big stat that you hear about in the media is the fact that in the study a 1 year old Labrador has equivalent aging to a 30 year old human based on it’s DNA!


Further, the study equivocates a 7 year old Labrador retriever to a 60-65 year old human based on the methyl method.


What’s the takeaway from this study with regards to the aging of senior dogs?


Dogs are likely becoming seniors far earlier than we think!

More studies are needed to give us more insight into how dogs age. However this study was very helpful in showing us something that I suspect many veterinarians already think. This study was limited to just one breed so performing this on the DNA of other breeds such as Dachshunds or Great Danes can help shed more light on how smaller vs giant breed dogs age. Overall this study was a great contribution to determining when senior dogs become seniors!


For those looking for a simple aging chart, consider downloading the free resource I created here.


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