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How Old is Your Dog?

Updated on September 29, 2021
Medically Reviewed by
Dr. Alam
Written by
Joel
2 sources cited
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For decades, dog owners have assumed that their pets aged about seven times as fast as their human counterparts. This made their one-year-old dog seven years old or their 10-year-old dog 70. A 100-year lifespan for a dog would be about 14 years old in human years.

It turns out this common belief is a misconception. Dogs do age faster than humans, but the process is not as easy as equating one human year to seven dog years.

How to Tell a Dog’s Age

According to a study published in the journal Cell Systems, the updated framework for assessing dog aging explains that the fastest aging period in a dog's life occurs within the first year. Each year after the aging process slows and the ratio of human-to-dog-years changes. In this new formula, the first eight weeks of a dog's life equals about nine months of a human infant's life.

Researchers compared epigenetic changes and development milestones in human and dog lives.

According to the information, the comparison of physiological milestones provides a better indication of a dog's age. They also compared end-of-life situations and estimated the average lifespan of a Labrador retriever of 12 years to be equivalent to the average 70-year lifespan of a human.

Additionally, most researchers and dog owners acknowledge that not all dogs age at the same rate. A certain dog’s lifespan is different from others. For example, Labs tend to stay in their “puppy phase” for as long as two years. Smaller breeds tend to live on average three to five years longer than larger breeds. And of course, as is the case with humans, diet and lifestyle affect a dog's aging process and how long he lives.

If you're wondering how old your dog is and you aren't sure how the new calculations work or if they apply to your dog due to its breed or a mix of breeds, read on to learn how to estimate your dog's age.

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Age Clues to Look For

There are several ways to assess how old a dog is. While the following clues may not tell you your dog’s exact age, but these can give you the approximate age of your pet. For instance:

Check Your Pet's Teeth

Examining the condition of your dog's teeth is a great way to get an idea of how old he is. According to the Humane Society of the United States, puppies develop teeth around four weeks of age. They still have their baby teeth, or milk teeth, up to eight weeks old. These small, sharp teeth begin to fall out and be replaced by adult teeth around three to six months.

How Old is Your Dog? 4

Dog's teeth begin to show wear around age one or two. This includes light stains and plaque, especially on the back teeth. Around three years of age, your dog's teeth will likely begin to yellow and have visible plaque. Five-year-old dogs tend to have a significant amount of tartar, and their teeth might start to wear down. This is usually around the time your vet will recommend professional dental cleaning.

In summary:

  • By 8 weeks: All baby teeth are present.
  • By 7 months: All permanent teeth are present, and they’re usually white and clean.
  • By 1-2 years: A dog’s teeth start to get dull, and there might be yellowing at the back teeth.
  • By 3-5 years: Tartar build-up is present, and some teeth may be showing some signs of wear.
  • By 5-10 years: Signs of tooth wear are more evident with signs of disease.

Examine Your Pet's Coat

Dog fur grays just like human hair as dogs grow older. The appearance of white or gray hairs around the muzzle and face can give you a clue about its age.

Most dogs begin to develop gray hair around seven or eight years of age. You may see gray hair in the muzzle area when your dog is five years old. Again, like humans, some dogs go gray prematurely. Your dog’s genetic makeup can cause this. Stress and anxiety also exacerbate the appearance of gray hair.

How Old is Your Dog? 5

Gaze Into Your Dog's Eyes

Older dogs tend to have cloudy eyes. Lenticular sclerosis is common, and discharge is more frequent as they age, too. Waning vision health is a normal part of the aging process for dogs. Old age causes the development of cataracts, and this can lead to blindness. Most dogs begin to experience a decrease in visual acuity around six to eight years of age. This seems young, but don't panic. It's akin to needing reading glasses in middle age for humans.

How Old is Your Dog? 6

Check Your Dog's Hearing

Have you noticed a decrease in your dog's response time? If he's growing older, it might be more about a hearing deficit than stubbornness. Younger dogs tend to have sharp hearing, but as they age, you'll need to speak more loudly for your pet to hear you. Your veterinarian can check your dog's hearing if you have any concerns.

Assess Your Dog’s Body Shape

As dogs grow older, their weight distribution changes. Try running down your hands down your dog's back. Do this on either side of their spine. This allows you to also check for muscle tone.

Older dogs have fat pads found on their lower back. Senior dogs will have more prominent spines. They may also appear sway-backed. These are due to mild muscle wasting.

Pay Attention to Your Dog's Activity Level

Like humans, most dogs slow down as they age. A young dog will be more active compared to an aging dog. The extra-exuberant puppy energy is completely a thing of the past for a senior dog. But most older-dog owners will tell you, every once in a while, they see signs of the puppy from years gone by.

This is especially common when you introduce a new puppy into your home. Few things will energize an older dog, like a new, younger friend.

Why Do Some Dog Breeds Live Longer than Others?

One of the primary differences between large breed and small breed dogs is how long the different-sized breeds live. The lifespan of large breed dogs is usually about 10 to 12 years. Smaller dogs usually live at least 11 years, but some live up to 14 or 15 years. Giant breeds have the shortest lifespan of about 7 to 8 years.

Researchers believe this is because large dogs use up their “growth energy” sooner than small breeds. This causes base damage to their cells because of oxidative stress. Smaller breeds have longer telomeres, which increases their lifespan.

Additionally, some research shows that breeds with long lifespans have a genetic resistance to potentially fatal diseases. Sometimes the length of your dog's life will have nothing to do with his size.

Breeds with a Shorter Lifespan

Giant breed dogs tend to have the shortest lifespans compared to small dogs. There are no guarantees, and your dog's diet and lifestyle affect his lifespan. In general, the breeds with the shortest lifespans (5 to 10 years) include:

  • Dogue de Bordeaux (5 to 7 years)
  • Great Dane (6 to 8 years)
  • Bernese Mountain Dog (6 to 8 years)
  • Irish Wolfhound (7 to 9 years)
  • Bullmastiff (7 to 10 years)
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What to Do When Your Dog Gets Older

You can't stop time, but you can slow your dog's aging process and ensure that he feels his best for as long as possible. Many senior dogs live happy, healthy lives and remain active well into their last years.

What can you do to help your dog live his best life as a senior?

  • See your vet at least annually. Older dogs might need more frequent visits.
  • Ask your vet to perform a body condition assessment to determine if your dog is at his ideal weight
  • Feed your dog a healthy, age-suitable diet that limits “human” food (fruits and veggies are ok)
  • Make sure your dog gets daily exercise, even if he's slow and tires quickly

How Can I Tell If My Dog is Aging Too Quickly?

The goal is to slow the aging process as much as you can for your pet. This ensures he lives as healthy as he can for as long as he can. If you have concerns your dog is aging too quickly, ask yourself the following:

  • Is your dog overweight? An overweight dog has a higher risk of certain diseases, especially as he gets older
  • Is your dog unenthusiastic? Your dog should be interested in his favorite activities, even as he gets older. If your dog has always loved going for car rides and suddenly he's not interested, it could be due to a health problem.
  • Is your dog sleeping a lot? Most house pets sleep a great deal more than non-pet owners expect, but there is such a thing as too much sleep for dogs. If your dog has always been lazier as some breeds tend to be, it's likely not a concern. But if you notice a gradual increase in sleep as your dog ages, it could be linked to arthritis or joint inflammation. Supplements can restore your dog's energy and help him balance sleeping and waking time.
  • Is your dog taking bathroom breaks and/or having bathroom accidents more than usual? If you notice your older dog suddenly has indoor potty accidents, increase the number of bathroom breaks. Just like humans, aging dogs tend to need the bathroom more frequently and even throughout the night. Keep in mind, an older dog's accident isn't the same training issue as it is with a young pup. Have your vet evaluate your older dog if potty accidents are a problem.
  • Does your dog have bad breath? Older dogs tend to have deteriorating dental health, which affects the smell of their breath. Brushing your dog's teeth daily or several times a week keeps tartar and plaque at bay and reduces the risk of many serious health problems.

There's no turning back time, but there are plenty of things you can do to help your dog age as slowly as possible. As your dog ages, make sure you understand how to help him feel his best and live as long as possible.

KNOW YOUR DNA REVIEWS

Best Dog DNA Test

We reviewed the top dog DNA test for finding out exactly which breed you have (and any relevant health and trait info you might need).

Resources

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HIDE

Coile, Caroline. “How to Feed the Senior Dog.” American Kennel Club, American Kennel Club, 28 Oct. 2016, www.akc.org/expert-advice/nutrition/how-to-feed-the-senior-dog/.

“NIH Researchers Reframe Dog-To-Human Aging Comparisons.” National Institutes of Health (NIH), 9 July 2020, www.nih.gov/news-events/news-releases/nih-researchers-reframe-dog-human-aging-comparisons.

Dr. Alam
Dr. Alam Roky
Medical Reviewer
Dr. Shamsul Alam Roky is a registered veterinarian who graduated from the Faculty of Veterinary, Animal, and Biomedical Sciences. Currently, he is working as a graduate research assistant at his university, in addition to running a private veterinary clinic named ‘Sylhet Veterinary Services” in his city.
Joel
Content Contributor
Joel is a writer with a passion for the science of DNA and the power of its manipulation.
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