Understanding a Dog’s Age

I learned recently that the idea dogs are "seniors at seven" comes from a study of border collies only, not a spectrum of how dogs age from different breeds. Researchers also often focus on beagles for these studies. One new paper, published in April 2021, suggests 6 new categories for understanding a dog's age. Let's take a look.


It turns out there really isn't a consistent model for classifying a dog's age throughout life. Because of that, it's hard for researchers to compare and use prior published papers on canine aging. 

There's debate about additional sub-categories. For example, dogs experience important changes during puberty and once they get over 12 or 14 years old. As a starting point, though, this timeline graphic helps you place your dog on an aging spectrum.

dogs age table for post about the new categories

How Dogs Age Categories

The study's authors explain that "These categories work to capture age-related developmental trajectories for the majority of dog breeds." These groups, they say, "support educational programs informing owners of what behavioral changes to expect in their dog as they age, but they cannot be used to reflect health-based needs associated with breed-specific mortality."

The 6 categories look like this:

  1. Puppy - 0-5 months
  2. Juvenile - 6-12 months 
  3. Young Adult - 13-24 months
  4. Mature Adult - 2-6 years
  5. Senior - 7-11 years (with these potential subcategories):
    7-9 years = early senior
    10-11 years = late senior
  6. Geriatric - 12-18+ years (with these potential subcategories):
    12-14 years = geriatric
    15-18+ years = very aged

Are Dogs Living Longer?

Apparently, there is a newer paper about dogs in the USA that discussed a "higher median longevity of 15.4 years" than an earlier study of dogs in the UK. So, that's interesting.

It does seem like my friends live with dogs who make it well into their teen years.

Heck, our ancient big boy Ginko made it to 4 months shy of his 16th birthday. That makes my new goal to get our current crew over 16. Before Ginko, the oldest dog I'd ever had was Penelope, a dalmatian who was 14 when we lost her.  

What About Giant Dogs?

Well, technically giant dogs die while still Mature Adults or very early Seniors, so older style canine aging tables where big dogs age more quickly and get called geriatric (when their brains and behaviors don't reflect such mental declines) "mask[s] the severity of the problems associated with early mortality in short-lived breeds," according to the paper's authors. 

They go on to say, "Morbidity and mortality when old are acceptable, indeed inevitable. However, when we see high morbidity and mortality in an animal that can be objectively classified as young, it should concern us."

What Does This Mean About How Dogs Age?

Well, dogs over age 12 tend to see "greater incidence of cognitive impairments" compared to dogs in their earlier senior years. And, dogs older than 15 "have a much higher incidence of cognitive impairment" than other senior dogs. 

Ginko experienced canine cognitive disfunction in his later years, including loss of housetraining (which was also caused by neurological issues) and random wandering the house, whining, barking, and sleep disruption. 

Definitely talk to your veterinarian if you start to see such changes in your older dog.

This special senior dog food with Medium Chain Triglycerides (MCT) did help Ginko, so I probably will transition our current dogs to it at some point as they age. (P.S. I no longer have a relationship with the dog food company, but I do feed Pro Plan. Also, that link is an old post. The giveaway is no longer live.)

Roxanne Hawn

Trained as a traditional journalist and based in the Rocky Mountains of Colorado, USA, I'm a full-time freelance writer for magazines, websites, and private clients. My areas of specialty include everything in the lifestyles arena, including health and home, personal finance and other consumer interests, relationships and trends, people and business profiles ... and, of course, all things pet related. I don't just love dogs. I need them in my life. Seriously.