How a Dog Ages and What You Can Expect at Each Life Stage

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By Deidre Grieves

When it comes to understanding how a dog ages, you may have heard that one dog year is equivalent to seven human years. But according to Dr. Lisa Lippman, a veterinarian based in New York City, that isn’t an exact calculation for determining dog age.

“The ‘seven-year rule’ is a simplified explanation of canine-human aging,” she says. According to Dr. Lippman, a medium-size dog that's well cared for will live roughly 1/7th as long as their owner, but different breeds of dogs age differently.

This guide will explain how a dog ages and how to best care for your dog at every life stage.

Dogs Age Based on Size and Breed

Dr. Lippman explains that the dog-years-to-human-years equation is actually more about weight than it is about age. “A 5-year-old dog that weighs 20 pounds or less is about 33 ‘human-years-old,’ where a dog that weighs over 90 pounds is closer to 41 years old in human years,” she says.

The dog age ranges associated with different life stages—puppy, adult and senior—vary depending on the size and breed of your pup. Most dogs, says Dr. Lippman, are considered puppies until they reach approximately 1 year old. But defining the transition between adult dogs and senior dogs is a little more complicated.

“Large dogs tend to age more quickly than their smaller counterparts,” she says. “Very large dogs may be considered seniors at 5 or 6 years of age, whereas small dogs aren’t seniors until 10 or 12 years old.”

Because of how dogs age, small dogs and large dogs also have different life spans. Smaller dogs like Chihuahuas, Yorkshire Terriers, Dachshunds and Pomeranians tend to live longer than larger dogs such as Saint Bernards, Great Danes, Newfoundlands and Irish Wolfhounds.

“While we still aren’t sure exactly what accounts for this difference in maturation and aging, smaller dogs definitely live longer, on average, than very large ones,” says Dr. Lippman. “This is especially apparent when you compare very small dogs, such as a Yorkshire Terrier—which can live well into their teens—with very large dogs like Great Danes—who live to be about 10.”

How to Determine Your Dog’s Age

While some shelters and rescues will list dog ages in their online descriptions and adoption paperwork, the age listed is usually only an estimate and is not always accurate.

“The best way to age your pet is by having your veterinarian take a look,” says Dr. Lippman. “Between their teeth and their blood work, we can usually give a pretty good estimation of age.”

Dr. Lippman says that pet parents should look at a dog’s teeth for signs of discoloration. If the teeth present yellowing or decay, your dog may be on the older side. If his teeth are white and healthy looking, he’s probably closer to a puppy than a senior.

Gray fur—especially around the muzzle and face—can also indicate aging, says Dr. Lippman.

Special Considerations for Each Life Stage

When it comes to caring for your dog, it’s important to tailor training and nutritional needs to his specific life stage. Follow these tips to make sure your dog has everything he needs for the best care.

Nutrition Requirements as Dogs Age

Canine dietary needs evolve as your dog ages. The dog food he eats may need to change as he transitions from a puppy to an adult to a senior dog.

“Puppies require more calories and fats to sustain their growing bodies,” says Dr. Lippman. “Adult dogs require the right combination of carbohydrates, fats and proteins. Senior dogs require fewer calories and less carbohydrates.”

There are age-specific dog food formulas available on the market, so make sure to consult your veterinarian about the type of food that is best for your dog and their age.

For puppies, consider Purina Pro Plan Focus Puppy chicken & rice formula dry dog food.

Older dogs can benefit from a senior diet that focuses on joint and brain health. You can consider Purina Pro Plan Bright Mind Adult 7+ chicken and rice formula for your senior pet.

Additionally, pet parents may want to talk to their vet about trying dog supplements to support their senior pet’s joint health, says Dr. Lippman. Ask your veterinarian about supplements containing ingredients like glucosamine and chondroitin, such as Zesty Paws Mobility Bites or NaturVet glucosamine DS plus MSM and chondroitin soft chews.

Supplements and certain diets for senior dogs can also assist in treating canine cognitive dysfunction (CCD), says Dr. Rachel Malamed, a veterinary behaviorist located in Los Angeles. “Medications, supplements and dietary therapy are often used for the treatment of CCD,” she says. “Many therapies contain elements such as antioxidants that decrease free radical damage in the brain, thus slowing progression of the disease.”

Behavioral Changes as Dogs Age

It should come as no surprise that puppies and senior dogs act very differently. Age-related behavioral changes are something pet parents should be prepared for and keep an eye on.

“A puppy may be more likely to display unruly jumping and mouthing behavior during greetings or to solicit attention. Puppies also need to chew, but as a result, destructive chewing of items, such as a pair of shoes, is common,” says Dr. Malamed.

“Often, these are self-rewarding or learned behaviors that are straightforward to address through positive reinforcement of desirable behaviors and offering alternate, more acceptable chewing options,” says Dr. Malamed. 

To satisfy your puppy’s urge to chew, Dr. Lippman suggests purchasing plenty of dog chew toys for puppies to keep young doggy mouths busy. The KONG puppy dog toy is a tough, stuffable dog treat toy for young pups. Teething puppies may also benefit from teething dog toys like the Nylabone puppy chew teething rings.

While puppies will show their age with tons of energy and lots of chewing, senior dogs may also show marked differences in their behaviors.

Canine cognitive dysfunction (CCD) is similar to Alzheimer’s disease in humans and can show up in senior dogs as they age with a variety of symptoms, says Dr. Malamed. “CCD is a neurodegenerative disease in senior dogs.” she says. “Clinical signs are often not recognized or [are] under-reported by owners.”

Dr. Malamed says that pet owners should watch for signs of canine cognitive dysfunction in dogs, including:

• Disorientation
• Reduced social interactions
• Increased anxiety and fear
• Sleeping more during the day
• Restlessness at night
• House soiling
• Pacing or wandering

“It is important to know that CCD is a diagnosis of exclusion,” says Dr. Malamed. “This means that in order to say that your dog has CCD, your vet must first rule out other diseases that mimic the various signs.”

General Care Tips for Each Life Stage

To keep your pet happy and healthy at every life stage, consider the following tips.

Besides providing your puppy with an outlet for chewing, “I am also a big supporter of crate training,” says Dr. Lippman. She recommends purchasing an adequately sized dog crate before you even bring your puppy home.

As adult dogs start to age, Dr. Lippman says that pet parents should keep a close eye on their pets to watch for changes and adjust care regimens accordingly.

“It’s important to be realistic about our dog’s abilities as they age. Older dogs may still be spry, but extra consideration should be given to their comfort,” Dr. Lippman says. She recommends investing in an orthopedic dog bed to help keep your senior pet comfortable. Also, dog ramps or stairs can help your senior pet get on top of furniture or other hard-to-reach areas safely.

Additionally, senior dogs may require more visits to the veterinarian throughout the year, and pet owners should be prepared for additional costs and time commitments that come with increased medical care.

Dogs of all ages need enrichment, says Dr. Malamed. “Dogs need to use their brains to maintain function, and enrichment has been shown to improve signs of brain aging,” she explains. “Enrichment in the form of puzzle games, food dispensing toys, novel toys and positive reinforcement training all help to provide mental and physical stimulation.”

For a fun dog interactive toy, try the Trixie activity flip board interactive dog toy or the ZippyPaws Burrow Squeaky Hide and Seek plush dog toy. Dog puzzle toys, including the Pet Zone IQ treat ball dog toy or the Nina Ottosson by Outward Hound dog brick interactive dog toy, are also potential enrichment tools.