by Dr. Jody Kaufman
Time seems to pass so quickly that it can take us by surprise when our pets show signs of aging. Under even the best circumstances, animals age at an accelerated rate compared to humans. The "seven years for one of ours" rule is a reasonable simplified estimate, but the rate of aging in dogs is based roughly on their size. A seven year-old Great Dane is geriatric, while a little poodle of the same age is only middle aged.
People often ask how long their pet will live. While we can give average life expectancies, every animal is an individual. Average human life expectancies may be in the eighties, but we all know of people who have succumbed to cancer in their forties or a heart attack in their fifties. Yet others are running marathons in their seventies. We see the same variability in our pets.
Dogs and cats suffer from many of the same age-related maladies that occur in people. Some breeds are predisposed to certain conditions or diseases. Degenerative arthritis is one of the most common problems in middle-aged and older dogs as well as many older cats. Heredity can play a major role in some breeds such as German Shepherd Dogs, Golden Retrievers and many others, but a large number of illnesses are related to obesity. A study was performed using Labrador Retrievers (one of the "at risk" breeds). The control group was fed a rationed amount and dogs in the other group were allowed to eat as much as they wanted. There was a significant increase in the number of dogs who developed arthritis, and they showed signs at a much earlier age.
Obesity influences the onset and severity of other diseases as well. Cats are especially prone to becoming diabetic if they are overweight. Owners may first notice an increased thirst and urine production. If the diabetes has been present for a while, the animal will start losing weight despite a normal or increased appetite. Dogs are more likely to become diabetic after repeated episodes of pancreatitis, a disease that is more likely to occur in overweight individuals. Certain hormonal conditions in dogs can also lead to diabetes. One is Cushing's disease, a disorder of the adrenal glands. While it can occur in any breed, we see it most commonly in Poodles, Boxers, Boston Terriers, Schnauzers, and Dachshunds.
Heart disease is fairly common in middle-aged and older dogs. The most common age-related heart problem arises from a thickening of the heart valves, termed endocardiosis. Initially the only sign is the appearance of a heart murmur, since the valves no longer make a tight seal. The murmur is the sound of blood turbulence during the contraction phase of the heart due to the leaky valves. Dogs may seem perfectly normal during the early stages of this type of heart disease. The heart muscle actually gets a little stronger since it has to work a little harder. Eventually, however, the heart begins to enlarge in ways that make the valvular regurgitation more severe. The first sign that owners may notice is a cough, followed by exercise intolerance and difficulty breathing. While heart disease is progressive, the rate can be extremely variable for different patients. Documenting the heart and lung sounds, taking baseline x-rays, and starting a low sodium diet may be all that we have to do for several years in many patients. In others the progression is more rapid, but there are medications that can help stabilize the condition.
The most common reason for the appearance of a heart murmur in a middle-aged or older cat is an overactive thyroid gland. Typically these cats start drinking and urinating more and losing weight despite an increased appetite. While these signs can mimic diabetes, the diseases are easily distinguished by blood tests and a urinalysis. While there are other reasons for the appearance of heart murmurs in cats, hyperthyroidism is our primary suspicion in patients over the age of eight.
All young dogs and cats have beautiful teeth. The age at which tartar and the subsequent periodontal disease start to develop probably depends more on genetics and general health than it does on diet. Some breeds such as Schnauzers, Maltese, small Poodles, Greyhounds, and others can have tartar beginning as early as two years of age, while an eight year-old Airedale might have beautiful teeth. The problems that ensue are more than aesthetic even though you can be knocked over by the breath of an animal with periodontal disease. Severe dental disease may play a role in kidney disease, since bacteria are released into the bloodstream every time the animal chews. The kidneys receive a fifth of the blood supply at any given time, which means that they can be barraged by bacteria. It's postulated that this is the reason that we see kidney infections (pyelonephritis) so commonly in elderly cats, when urinary infections are quite rare in younger cats. (The common cystitis or feline lower urinary tract disease is usually a sterile inflammation.) This is why getting a youngster to accept tooth brushing can be so important in later years, as can a thorough dental cleaning if home prophylaxis hasn't been enough to prevent periodontal disease. A vaccine has recently been developed for dogs that helps control the bacteria that are instrumental in causing periodontal disease.
Some degree of kidney dysfunction is common in elderly animals, especially cats. The first signs are so subtle that they may be overlooked; there may be a slight increase in thirst and urination as the kidneys lose their ability to concentrate urine. There are various causes for kidney failure, but they all end the same way. However, diet and medication can stabilize and at times reverse some of the changes.
Cancer is a threat to elderly animals as well as people. This is another disease that can display a predilection for certain breeds. Boxers and Golden Retrievers are especially vulnerable, though cancer can occur in any breed. How do we detect it? Skin masses are visible, a visual exam or fine needle aspirate (looking at the cells through a microscope) may tell us whether or not we need to worry. Lipomas are extremely common in middle-aged and elderly dogs. They are collections of fat cells, which can grow quite large. They are benign, although especially large ones can interfere with movement. Other tumors are not visible, but may cause signs related to the organ that they are affecting. Difficulty breathing, vomiting, weight loss, lethargy, abdominal distension, anemia...the list is virtually endless. Some cancers have a good prognosis if removed early, while others are aggressively malignant.
Old age is not a disease. Yet there are many diseases that occur as our animal companions get older. Many problems can be alleviated or slowed down by early detection. This is the reason we believe that a thorough physical exam as well as blood and urine screening is beneficial in our middle-aged and geriatric patients. Ultimately we all succumb to some malady, but our aim is to help our pets have the best quality of life for as long as possible.