Aging in dogs
Image:10 yr old Mastiff.JPG|thumb|250px|Older dogs, similar to this 10-year-old Neapolitan Mastiff, often grow grey hairs on their muzzles, and some dogs grow grey hair all over.
Not all dogs gain grey hair when aging.
Aging in dogs varies from breed to breed, and affects the dog's health and physical ability. As with humans, advanced years often bring changes in a dog's ability to hear, see, and move about easily. Skin condition, appetite, and energy levels often degrade with geriatric age. Medical conditions such as cancer, kidney failure, arthritis, dementia, and joint conditions, and other signs of old age may appear.
The aging profile of dogs varies according to their adult size : smaller breeds have an average lifespan of 10–15 years, with some even exceeding 18 years in age; medium breeds typically live for 10 to 13 years; and giant [dog breed]s have the lowest minimum lifespan, with an overall average of 8 to 13 years. The latter reach maturity at a slightly older age than smaller breeds, with giant breeds reaching adulthood at around two years old compared to the norm of around 13–15 months for other breeds. The accelerated rate of growth required by the drastic change in size exhibited in giant breeds is speculated by scientists at the American Kennel Club to lead to a higher risk of abnormal cell growth and cancer.
Terminology
The terms dog years and human years are frequently used when describing the age of a dog. However, there are two diametrically opposed ways in which the terms are defined:- One common nomenclature uses "human years" to represent a strict calendar basis and a "dog year" to be the equivalent portion of a dog's lifetime, as a calendar year would be for a human being. Under this system, a 6-year-old dog would be described as having an age of 6 human years or 40–50 dog years.
- The other common system defines "dog years" to be the actual calendar years of a dog's life, and "human years" to be the equivalent age of a human being. By this terminology, the age of a 6-year-old dog is described as 6 dog years or 40–50 human years, a reversal from the previous definition.
Aging profile
Dog age concepts can be summarized into three types:- Popular myth — It is popularly believed that one human year equals seven dog years. This is inaccurate since dogs are able to reproduce from the age of 1.
- One size fits all — A rule of thumb is that the first year of a dog's life is equivalent to 15 human years, the second year equivalent to 9 human years, and each subsequent year about 5 human years. So, a dog age 2 is equivalent to a human age 24, while a dog age 10 is equivalent to a human age 64. This is more accurate but still fails to account for size/breed, which is a significant factor.
- Size- or breed-specific calculators — These try to factor in the size or breed as well. These are the most accurate types. They typically work either by expected adult weight or by categorizing the dog as "small", "medium", or "large".
Oxidative stress appears to be a significant determinant of longevity in small breed compared to large breed dogs. Oxidative damage to DNA can be measured by assessing the level of 8-Oxo-2'-deoxyguanosine in DNA. Oxidative DNA damage measured in puppies was found to be higher in larger dog breeds with shorter lifespans than in smaller breed dogs with longer life spans. This result suggested that DNA repair mechanisms fail earlier in larger breed dogs so that more DNA damage is accumulated sooner in these breeds leading to reduced longevity.
Emotional maturity occurs, as with humans, over an extended period of time and in stages. As in other areas, development of giant breeds is slightly delayed compared to other breeds, and, as with humans, there is a difference between adulthood and full maturity. In all but large breeds, sociosexual interest arises around 6–9 months, becoming emotionally adult around 15–18 months and fully mature around 3–4 years, although as with humans learning and refinement continue thereafter.
According to the UC Davis Book of Dogs, small-breed dogs become geriatric at about 11 years; medium-breed dogs at 10 years; large-breed dogs at 8 years; and giant-breed dogs at 7 years.
Life expectancy by breed
Life expectancy usually varies within a range. For example, a Beagle usually lives to around 12–15 years, and a Scottish Terrier usually lives to around 10–16 years. The longest living verified dog is Bluey, an Australian Cattle Dog who died at 29 years. Bobi, a male purebred Rafeiro do Alentejo, was claimed to have died at age 31 in 2023.Two of the longest living dogs on record, "Bluey" and "Chilla", were Australian Cattle Dogs. This has prompted a study of the longevity of the Australian Cattle Dog to examine if the breed might have exceptional longevity. The 100-dog survey yielded a mean longevity of 13.41 years with a standard deviation of 2.36 years. The study concluded that while Australian Cattle Dogs are a healthy breed and do live on average almost a year longer than most dogs of other breeds in the same weight class, record ages such as Bluey's or Chilla's should be regarded as uncharacteristic exceptions rather than as indicators of common exceptional longevity for the entire breed.
A random-bred dog has an average life expectancy of 13.2 years in the Western world.
Some attempts have been made to determine the causes for breed variation in life expectancy.
Sorted by breed or life expectancy
The following data is from a 2024 study published in Scientific Reports. The total sample size for his study was about 584,734 unique dogs located in the UK, of which 284,734 were deceased.Factors affecting life expectancy
Apart from breed, several factors influence life expectancy:- Frequency of feeding — Researchers associated with the Dog Aging Project report that dogs that are fed just once daily are healthier on average than dogs fed more frequently. Dogs that received one meal per day had fewer disorders of their dental, gastrointestinal, musculoskeletal, kidney, and urinary systems.
- Diet — There are some disagreements regarding the ideal diet. Commonly, senior dogs are fed commercially manufactured senior dog food diets. However, at least two dogs died at 27 years old with non-traditional diets: a Border Collie who was fed a purely vegetarian diet, and a bull terrier cross fed primarily kangaroo and emu meat. They died only 2 years and 5 months younger than the second oldest reported dog, Bluey.
- Spaying and neutering — According to a study by the British Veterinary Association, "Neutered females lived longest of dogs dying of all causes, though entire females lived longest of dogs dying of natural causes, with neutered males having the shortest lifespan in each category." Neutering reduces or eliminates the risk of some causes of early death, for example pyometra in females, and testicular cancer in males, as well as indirect causes of early death such as accident and euthanasia, but there might increase the risk of death from other conditions in males, and neutered males might have a higher rate for urinary tract cancers such as transitional cell carcinoma and prostatic adenocarcinoma. Caution should be used when interpreting the results of these studies. This is especially important when you consider the frequency of transitional cell carcinoma and prostate carcinoma in a male dog versus the chance an intact male dog will succumb to death from roaming, benign hyperplasia of the prostate causing prostatic abscesses or inability to urinate or euthanasia due to fighting or aggression.
A major study of dog longevity, which considered both natural and other factors affecting life expectancy, concluded that:
In 2024, a study published in the journal Scientific Reports involving 584,734 British dogs across over 150 breeds revealed that larger breeds and those with flattened faces tended to have shorter average lifespans compared to smaller dogs and breeds with elongated snouts. Female dogs were found to live slightly longer than male dogs.
Effects of aging
In general, dogs age in a manner similar to humans. Their bodies begin to develop problems that are less common at younger ages, they are more prone to serious or fatal conditions such as cancer, stroke, etc. They become less physically active and less mobile and may develop joint problems such as arthritis. They also become less able to handle change, including wide climatic or temperature variation, and may develop dietary or skin problems or go deaf. In some cases incontinence may develop and breathing difficulties may appear.In studies of cognitive abilities in aging dogs, it has been shown that qualities such as problem-solving, boldness and playfulness tend to decline with age. However, in tasks involving high motivation and low physical demands, older dogs have learned to perform a new task just as well as younger ones. In old age dogs may develop dementia, which is associated with amyloid-beta, a misfolded protein that has been observed in both dogs and humans.
The most common effects of aging are:
- Loss of hearing
- Loss of vision
- Decreased activity, more sleeping, and reduced energy
- Weight gain
- Weakening of immune system leading to infections
- Skin changes
- Change in feet and nails
- Arthritis, dysplasia and other joint problems
- Loss of teeth
- Gastrointestinal upset
- Weakness in muscles and bones
- Urinary issues
- Mammary cysts and tumors in females
- Dementia
- Heart murmurs
- Diabetes
Importance of diet in aging
By changing the nutrition of a dog's diet as it ages, certain ailments and side effects of aging can be ameliorated.Some proposed nutrients and ingredients in senior dog diets include:
- Good sources of protein to meet higher protein requirements
- Glucosamine and chondroitin sulfate to help maintain joint and bone health
- Omega-3 fatty acids for joint and bone health as well as maintaining immune system health
- Calcium and phosphorus for maintenance of bone structure
- Beet pulp and flaxseed for gastrointestinal health
- Fructooligosaccharides and mannanoligosaccharides work to improve the health of the gastrointestinal tract by increasing the number of "good" bacteria and decreasing the amount of "bad" bacteria
- Appropriate levels of vitamin E and addition of L-carnitine to support brain and cognitive health
- Dietary antioxidants such as vitamin E.