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 dogs often live over 15–16 years
(sometimes longer than 20 years), medium and large size dogs typically 10 to
20 years, and some giant dog breeds such as mastiffs, often only 7 to 8 years.