Aging in dogs

Aging in dogs covers the impact of aging in the domestic dog (Canis lupus familiaris), common medical and clinical issues arising, and life expectancy.

  Canine conditions such as temperature, change, hearing, and skin condition often degrade with geriatric age, and medical conditions such as cancer, renal failure, arthritis 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 dogs often live over 15 - 16 years, medium and large size dogs typically 10 to 13 years, and some giant dog breeds such as mastiffs, often only 7 to 8 years. The latter also mature slightly older than smaller breeds - giant breeds becoming adult around two years old compared to the norm of around 12 - 15 months for other breeds.

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Aging profile

  A variety of calculators to convert "dog years" to human years have been proposed and can be found on the Internet. They can be summarized into three types:

• "Popular myth" - popular myth suggests that "one human year equals seven dog years" or the like. This is inaccurate on two scores, since the first year or two years representing some 18-25 years, and the ratio varies with size and breed.
• "One size fits all" - suggests that the first two years equal 10.5 years each, with subsequent years equalling four human years. This is more accurate but still fails to allow for size/breed, which is a significant factor.
• Size/breed specific calculators - which try to factor in the size or breed as well. These are the most accurate types. They typically either work by expected adult weight [1], or by categorizing the dog as "small, medium, large".

No one formula for dog to human age conversion is scientifically agreed, although within fairly close limits they show great similarities.

As a rough approximation, the human equivalent of a one-year-old dog is between about 10 and 15 years—a one-year-old dog or cat has generally reached its full growth and is sexually mature, although it might still be lanky and need to fill in a more mature musculature, similar to human teenagers. The second year is equivalent to about another 3 to 8 years in terms of physical and mental maturity, and each year thereafter is equivalent to only about 4 or 5 human years.^[2]

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, socio-sexual interest arises around 6-9 months, becoming emotionally adult around 15-18 months, and full maturity around 3-4 years, although as with humans learning and refinement continues thereafter.

According to the UC Davis Book of Dogs, small-breed dogs (such as small terriers) then 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.^[3]

Life expectancy by breed

Accidents aside, 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.^[4]

A random-bred dog (also known as a mongrel) has an average life expectancy of 13.2 years in the USA and much of Europe.

Sorted by breed

These data are from Michell (1999).^[5] The total sample size for his study was about 3,000 dogs, but the sample size for each breed varied widely. For most breeds, the sample size was low. For a more comprehensive compilation of results of longevity surveys, see the breed data tables at the Dog Longevity web site.

Sorted by expectancy

Factors affecting life expectancy

Apart from breed, several factors influence life expectancy:

• Diet - although there is some disagreement as to the ideal diet. The oldest dog on record was Bluey, an Australian Cattle Dog, who died at 29 in 1939. In the 2000s, at least two dogs were still living at 27 or 28 years old, but one was fed a purely vegetarian diet^[6] and one fed primarily on kangaroo and emu meat^[7].
• Spaying and neutering - according to a study by the British Veterinary Association (author AR Michell is the president of the Royal College of Veterinary Surgeons), "Neutered bitches lived longest of dogs dying of all causes, though entire bitches lived longest of dogs dying of natural causes, with neutered males having the shortest lifespan in each category." ^[5] Neutering reduces or eliminates the risk of some causes of early death, for example pyometra in bitches, and testicular cancer in males, as well as indirect causes of early death such as accident and euthanasia (intact dogs may roam more and be more aggressive), but also raises the risk of death from other conditions (castration favors prostate cancer in males, and neutered males have the highest rate for this condition^[8]).

A major study of dog longevity, that considered both natural and other factors affecting life expectancy, concluded that:

"The mean age at death (all breeds, all causes) was 11 years one month, but in dogs dying of natural causes it was 12 years eight months. Only 8 per cent of dogs lived beyond 15, and 64 per cent of dogs died of disease or were euthanased as a result of disease. Nearly 16 per cent of deaths were attributed to cancer, twice as many as to heart disease. [...] In neutered males the importance of cancer as a cause of death was similar to heart disease. [...] The results also include breed differences in lifespan, susceptibility to cancer, road accidents and behavioural problems as a cause of euthanasia." ^[5]

Effects of aging

In general, dogs age in a manner similar to humans. Their bodies begin to develop problems which are less common at younger ages, they are more prone to serious or fatal conditions such as cancer, stroke, and the like, they become less mobile and may develop joint problems such as arthritis, and in old age often become less physically active. Additionally, they 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.

"Aging begins at birth, but its manifestations are not noticeable for several years. The first sign of aging is a general decrease in activity level, including a tendency to sleep longer and more soundly, a waning of enthusiasm for long walks and games of catch, and a loss of interest in the goings on in the home." ^[9]

The most common effects of aging are:^[10]

• Loss of hearing
• Loss of vision (cataracts)
• Decreased activity, more sleeping, and reduced energy (in part due to reduced lung function)
• Weight gain (calorie needs can be 30-40% lower in older dogs)
• Weakening of immune system leading to infections
• Skin changes (thickening or darkening of skin, dryness leading to reduced elasticity, loss or whitening of hair)
• Change in feet and nails (thicker and more brittle nails makes trimming harder)
• Arthritis and other joint problems
• Loss of teeth
• Gastrointestinal upset (stomach lining, diseases of the pancreas, constipation)
• Urinary issues (incontinence in both genders, and prostatitis/straining to urinate in males)
• Mammary cysts and tumors in females
• Senility
• Heart murmurs
• Diabetes ^[11]

Illnesses

Behavior, needs and adaptability

Handling aging in dogs

"A dog that enjoyed his puppyhood and his mature years should have the opportunity to enjoy his aging years as well. If he has been a happy-go-lucky, independent critter for six or eight or 10 years before signs of aging become overt, let him set his own limits for as long as possible. He'll probably do a better job than you will." [9]

As a dog moves from midlife to old age and becomes geriatric, there are some specific measures which can help to keep a good quality of life and help the older dog remain in the best condition possible: ^[9]

• Dogs which are stiff in the morning may benefit from gently walking it out, with coaxing if necessary.
• Provide a thick, soft surface to lie and sleep on, if they want one.
• The skin may dry out, if this happens more frequent brushing can stimulate natural oils, or else ask a vet for advice.
• Older dogs have less resistance to parasites and infection, so watch more carefully for ticks and fleas.
• As their activity level reduces, also reduce their food intake (and particularly fatty foods) to ensure they don't put on weight. Extra weight - as with humans - is a factor in many health conditions.
• A dog may be accustomed to climbing stairs or furniture which they no longer can do with ease. Balance their need to be close to their family, with their ability to manage obstacles, and the risk of incontinence if they cannot easily reach a "safe location". Consider baby gates, or ramps, which are commonly available.
• Do not scold dogs angrily for accidents which they are unable to easily avoid (incontinence, clumsiness, and so on). As with humans, control and co-ordination may be less smooth than in their prime of life.
• Allow them their sleep. They may not adapt to suddenly being woken up in an abrupt manner, and may snap slightly if this is unexpected and happens during a deep sleep or dream.
• Continue to provide ongoing training and activities for their enjoyment and mental stimulation. These might include refresher courses, outings and the like.
• Check with a veterinarian for advice on their general health, including digestive upsets.

Other common changes include being aware of changes to their attention, behavior and body. For example, skin conditions can often be noticed by familiarity with their feeling, as gained through stroking and exploring their fur. Dull eyes or appearance of anxiety may indicate pain. Sudden changes to digestion or activity level may indicate organ or diet issues that can often be treated.

References

See also

• Aging
• Old age
• Pet loss