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 (often determined by their breed): 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 breeds 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 (365 days) 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 (depending on the breed) dog years. The other common system defines "dog years" to be the actual calendar years (365 days each) 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.
However, regardless of which set of terminology is used, the relationship between dog years and human years is not linear, as the following section explains.
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 general rule 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".
No one formula for dog-to-human age conversion is scientifically agreed on, although within fairly close limits they show great similarities. Researchers suggest that dog age depends on DNA methylation which is an epigenetic process. Epigenetic changes occur nonlinear in dogs compared to human.
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 (compare humans age 20 and age 40 for example). 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 (such as small terriers) become geriatric at about 11 years; medium-breed dogs (such as larger spaniels) at 10 years; large-breed dogs (such as German Shepherd Dogs) at 8 years; and giant-breed dogs (such as Great Danes) at 7 years.Siegal, Mordecai (Ed.; 1995). UC Davis School of Veterinary Medicine Book of the Dogs; Chapter 5, "Geriatrics", by Aldrich, Janet. Harper Collins. .
Life expectancy by breed Life expectancy usually varies within a range. For example, a Beagle (average life expectancy 13.3 years) usually lives to around 12–15 years, and a Scottish Terrier (average life expectancy 12 years) 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.World's oldest pooch dies, Beaver County Times, 13 March 1984. Retrieved 9 May 2011. 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.Lee, P. (2011). Longevity of the Australian Cattle Dog: Results of a 100-Dog Survey. ACD Spotlight, Vol. 4, Issue 1, Spring 2011, 96–105. http://www.acdspotlight.com/ 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 (also known as a mongrel or a mutt) 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.
Breed Expectancy (years) Lancashire Heeler 15.4 Tibetan Spaniel 15.2 Bolognese 14.9 Shiba Inu 14.6 Papillon 14.5 Havanese 14.5 Lakeland Terrier 14.2 Coton de Tulear 14.2 Border Terrier 14.2 Schipperke 14.2 Large Munsterlander 14.1 Lhasa Apso 14 Swedish Vallhund 14 German Spitz Mittel 14 Norwich Terrier 14 Australian Cattle Dog 14 Poodle 14 Cairn Terrier 14 Italian Greyhound 14 Miniature Dachshund 14 Welsh Springer Spaniel 14 Lowchen 13.9 Bearded Collie 13.9 Belgian Tervuren 13.8 Parson Russell Terrier 13.8 Finnish Lapphund 13.8 Bracco Italiano 13.8 Welsh Terrier 13.8 Tibetan Terrier 13.8 Australian Shepherd 13.7 Miniature Pinscher 13.7 Soft Coated Wheaten Terrier 13.7 Bedlington Terrier 13.7 Spanish Water Dog 13.7 Petit Basset Griffon Vendeen 13.7 Wire Fox Terrier 13.5 English Springer Spaniel 13.5 Irish Terrier 13.5 Norfolk Terrier 13.5 Sussex Spaniel 13.5 Vizsla 13.5 Chinese Crested 13.4 Whippet 13.4 Shetland Sheepdog 13.4 West Highland White Terrier 13.4 German Shorthaired Pointer 13.4 Brussels Griffon 13.3 Miniature Schnauzer 13.3 American Cocker Spaniel 13.3 Collie 13.3 Jack Russell Terrier 13.3 Silky Terrier 13.3 Puli 13.3 Yorkshire Terrier 13.3 English Cocker Spaniel 13.3 Tibetan Mastiff 13.3 Saluki 13.3 Pekingese 13.3 Dalmatian 13.2 Dachshund 13.2 Nova Scotia Duck Tolling Retriever 13.2 Polish Lowland Sheepdog 13.2 Pembroke Welsh Corgi 13.2 Golden Retriever 13.2 Cardigan Welsh Corgi 13.1 English Setter 13.1 Border Collie 13.1 Field Spaniel 13.1 Sealyham Terrier 13.1 Labrador Retriever 13.1 Samoyed 13.1 Maltese 13.1 Toy Manchester Terrier 13 Foxhound 13 German Wirehaired Pointer 13 Standard Schnauzer 13 Japanese Spitz 13 Portuguese Water Dog 13 Norwegian Elkhound 13 Toy Fox Terrier 12.9 Irish Setter 12.9 Weimaraner 12.8 Dandie Dinmont Terrier 12.8 Shih Tzu 12.8 Scottish Terrier 12.7 Briard 12.6 Beagle 12.5 Basset Hound 12.5 American Staffordshire Terrier 12.5 Bichon Frise 12.5 Japanese Chin 12.5 Kerry Blue Terrier 12.4 Gordon Setter 12.4 Skye Terrier 12.4 Keeshond 12.3 Clumber Spaniel 12.3 Miniature Bull Terrier 12.2 Pomeranian 12.2 Curly-Coated Retriever 12.2 Old English Sheepdog 12.1 Chow Chow 12.1 Basenji 12.1 Giant Schnauzer 12.1 Glen of Imaal Terrier 12.1 Crossbreed 12 Airedale Terrier 12 Bull Terrier 12 Canaan Dog 12 Staffordshire Bull Terrier 12 Belgian Malinois 12 Borzoi 12 Kelpie 12 Rhodesian Ridgeback 12 Spinone Italiano 11.9 Siberian Husky 11.9 Chihuahua 11.8 Cavalier King Charles Spaniel 11.8 Boston Terrier 11.8 Flat-Coated Retriever 11.7 Pug 11.6 Chesapeake Bay Retriever 11.6 Greyhound 11.5 Akita 11.4 German Shepherd Dog 11.3 Boxer 11.3 American Eskimo Dog 11.3 Alaskan Malamute 11.3 Bouvier des Flandres 11.3 Doberman Pinscher 11.2 Afghan Hound 11.1 Brittany 11.1 Dogue de Bordeaux 11.1 Newfoundland 11 Great Pyrenees 10.9 Black Russian Terrier 10.9 Irish Water Spaniel 10.8 Chinese Shar-Pei 10.6 Rottweiler 10.6 Great Dane 10.6 Scottish Deerhound 10.5 Bullmastiff 10.2 Anatolian Shepherd 10.1 Bernese Mountain Dog 10.1 Leonberger 10 Pharaoh Hound 10 Irish Wolfhound 9.9 Bulldog 9.8 French Bulldog 9.8 Affenpinscher 9.3 Bloodhound 9.3 Neapolitan Mastiff 9.3 Saint Bernard 9.3 Mastiff 9 Cane Corso 8.1 Presa Canario 7.7 Caucasian Shepherd Dog 5.4
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,Vegetable-Eating Dog Lives to Ripe Old Age of 29; Also: Who is the Oldest Dog in the World; 1.8 Years Longer 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.