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How Old is Old? Comparing Dog Age to Human Age

dog_to_human_yearsYou watch your young pup bounce across the lawn. You see your old dog lumber slowly to the food bowl. You take a brisk run with your young dog close at your heels. You slowly walk to the mailbox and your old dog still lags behind. 

What a difference a few years make to your dog. You don’t feel older, so why does your dog? Perhaps it’s because what you and your dog consider “old” are vastly different. Comparing your human age to your furry friend’s canine age is rather complicated, but, simply put, one year to Fido is not one year to you.

 

Doing the Math

The most common theory comparing human and canine ages uses this equation: Dog years X 7 = Human years. This simple equation is only a rough estimate. A more accurate comparison of human vs. canine age takes into consideration the dog’s size and breed.

"A more accurate comparison of human vs.
canine age takes into consideration
the dog’s size and breed"

Smaller dogs age more slowly and have longer life spans. Larger dogs age more quickly and have shorter life spans. In addition, certain breeds enjoy more longevity than others. When comparing size, small Poodles live longer than huge Great Danes. But when comparing breed, Great Danes outlive mid-sized Bulldogs.  So the 7 to 1 ratio doesn’t hold across the board.

"Dogs develop more quickly the first two years
of life, after which development levels out a bit."

Another factor that skews age calculation involves the rate of canine development. Dogs develop more quickly the first two years of life, after which development levels out a bit. During the first two years, one dog year equals about 10.5 human years. So the dog:human ageing ratios is 10.5:1 rather than 7:1. When a dog hits the three year mark, he ages 4 years to every 1 human year bringing the ratio to 4:1. So a 10 year old dog is basically the equivalent of a 53 year old human. Using the simple equation, this same 10 year old dog would be 70 years old.

All of these calculations are based on the assumption that the average human life expectancy in developed countries is 80 years. The average life span globally is only 66 years. So the equations have to be altered according to geography. Complicated enough for you?

 

Why simple math won’t work

"Complications in comparing dog age
to human age are well founded"

Complications in comparing dog age to human age are well founded. The old 7 dog years =1 human year theory is inaccurate because the dog ages and develops more quickly the first two years of life. Plus the ratio varies with dog breed and size.  Even the more accepted equation utilizing the 10.5 factor the first two years of the dog’s life and 4 years thereafter has pitfalls because it doesn’t account for size and breed. The more accurate estimate of a dog’s age in human years is calculated taking size and breed into consideration. This method either categorizes dogs as small, medium, and large or more specifically uses their estimated adult weight.

 

So, what’s the answer to the math problem?

Who knows?  The easiest equation (7:1) is probably the least accurate. Formulas that take into consideration the faster development that occurs the first two years of life give a more accurate comparison. But even with this theory, there is variation. Some mathematicians feel that a one year old dog should be compared to a 10-15 year old human. The second year, as development levels out, should equate to 3 to 8 years of human ageing. That would put a two year old dog on par with a 13-23 year old human.  But that’s still a big range.

"What is consistent is the fact that dogs age
more rapidly than their owners do."

In short, there is no definitive answer to the math problem. There is just too much variability in the canine community. Too many breeds. Too many sizes.  What is consistent is the fact that dogs age more rapidly than their owners do. What is consistent is the fact that a one year old dog often resembles a gangly teenager. What is consistent is that a 4 year old dog has the energy of a young adult. What is consistent is that a 9 year old dog walks with the stiff gait of a senior citizen.

 

Emotional Ageing

To further complicate the issue, emotional maturity doesn’t align with physical maturity. Emotional maturity occurs over an extended period of time.  For example, a 21 year old human is considered an adult, but may not reach emotional maturity until age 40 or so. The same applies to dogs. Even though a nine month old pup may be socially and sexually active, full maturity isn’t achieved until age 3 or 4.  That’s why 2 year old Labradors still chew your favorite slippers!

 

So, what is old?

When is senior status conferred? For humans, some people consider 55 year olds to be senior citizens. Others delay imposing that status until 65 years. Canine senior status varies, too. Small dogs are considered senior citizens of the canine community when they reach 11 years of age. Their medium sized friends become seniors at 10 years of age. Their larger sized colleagues are seniors at 8 years of age. And, finally, their giant-breed counterparts are seniors at 7 years old. So a Great Dane becomes a senior citizen far earlier than a Pomeranian.

 

Signs of Ageing

Like humans, dogs suffer the effects of ageing including:

  • Loss of vision
  • Loss of hearing
  • Weight gain
  • Loss of energy
  • Arthritis and other joint problems
  • Loss of muscle tone
  • Loss of teeth
  • Loss of organ integrity (heart, liver, kidneys)
  • Loss of skin elasticity
  • Loss of hair
  • Loss of immunity
  • Loss of mental acuity

With age comes lots of loss, but there is also a lot of fulfillment looking back on a life (human or canine) that was well-lived. So forget about the equations. The joy you share with your pet should never get old.

This client information sheet is based on material written by: Lynn Buzhardt, DVM

© Copyright 2016 LifeLearn Inc. Used and/or modified with permission under license.