The Canine Aging Process

Older dogs benefit from developments in veterinary geriatric medicine.


By Randy Kidd, DVM, PhD

Aging is a natural process of all animals, and of all cells, tissues, and organs within the animal. Every individual animal ages at a different rate, and each type of tissue or organ system has its normal rate of proceeding through the aging process.

Geriatrics is the branch of medicine that treats all problems peculiar to old age and aging, including the clinical problems of senescence (the process or condition of growing old, especially the conditions resulting from the transitions and accumulations of the deleterious effects of the aging process) and senility (the physical and mental deterioration associated with old age).

Death, dying, mortality, and immortality are prime fodder for philosophers, poets, musicians, and spiritual gurus. In our Western culture we tend to want to keep it that way. Until recently, most scientists and health professionals have been loath to discuss death or dying, leaving these subjects to mystics and philosophers.

Recent years, however, have produced a spate of interest in aging and anti-aging medicines. Geriatrics as a specialty is only 20 or 25 years old, and research interest in aging goes back only another 15 years before that. This newfound interest has created fertile field for anti-aging innovations – as well as the perfect weed bed for charlatans who will try to convince you they can lead you and your pets to the fountain of youth.

How and when dogs die
Not too many years ago, the two main reasons for the death of pet dogs were trauma and infections. Better hygiene, an understanding of proper nutrition, and better healthcare in general have all worked together to lessen the impact of infectious diseases, and leash laws and better training methods have helped to keep traumatic causes of death to a minimum.

Today our primary concern for the aging animal is chronic disease, but while chronic diseases do have their impact on lifespan, we also need to consider that many of these diseases and life itself simply wear out the cells of the body, and eventually the body itself.

In addition, we need to remember that the number one killer of dogs in this country is euthanasia – most often due to behavioral problems that the dog’s caretaker couldn’t or wouldn’t take care of. Every year millions of dogs are killed before they could reach old age because it was felt they did not fit into our society. This is an unfortunate fact of life in this country.

Finally, another fact of life is that we can never know exactly when our best buddies are going to die, nor when we will die. For some folks this is sheer misery; for others it is reassuring – and it is this very fact of life that makes some of us two-leggeds want to live every day the way our pets who don’t know about mortality do: fully, with joy and unreserved passion.

The natural process of aging
Common diseases of the geriatric dog (i.e., diseases that seem more prevalent in the aged dog than in younger critters) include diabetes mellitus, prostatic disease, obesity, cardiovascular disease, cataracts, dental disease, keratoconjunctivitis sicca, hypothyroidism, urolithiasis, hyperadrenocorticism, anemia, urinary incontinence, hepatopathies (liver conditions), chronic renal disease, and a long list of chronic degenerative diseases.

While this list may seem daunting, a closer look reveals that almost all the “diseases” are caused by diminished function of one or more organ systems – the inevitable and natural consequence of aging. Further, almost all these diseases can be slowed in their progress, and in all cases there are certainly ways to ease your dog through the disease and help provide a decent quality of life.

Some “geriatric” symptoms include:

• Weakness, lethargy

• Coughing, difficulty breathing, or exercise intolerance; seems winded after walking or playing

• Increased thirst and/or increased urination; has frequent accidents or urinates in his bed while sleeping

• Stiff, has difficulty getting up or down, or is sore after running and playing

• Seizures

• Poor haircoat – dry and brittle skin and/or haircoat, flaky skin

• Eating habits have changed – perhaps due to a poor sense of smell and/or taste

• Sudden weight loss or gain

• Bad smelling breath and/or red and irritated gums

• Sometimes seems disoriented or is slow to respond

• Crotchety attitude in a normally pleasant dog; doesn’t want to be bothered, and lets you know it

• Just isn’t acting like him/herself

Part of the problem with trying to define old age is that each organ system has its own timeline for aging, and each will exhibit its own way to show it is growing old. Following are some examples of how specific organ systems tend to age.

• Skin: As the skin ages, it becomes less pliable or elastic. The human face demonstrates this “hardening” of the skin with the appearance of wrinkles. The surface of the dog’s skin also tends to dry out, and the hair begins to gray, usually beginning at the dog’s muzzle and eyes. These changes make the skin more susceptible to outside irritants, and minor skin irritations are more likely to create a population of skin cells (keratinocytes) that grow into tumor cells.

• Eyes: Many older dogs develop a cloudiness of the eyes (senile cataract) that is the result of a disruption of the normal arrangement of the tissue fibers in the lens. This creates a loss of transparency and reduction of vision. This cloudiness varies in intensity, and the lens opacity may eventually proceed to the point where the dog is blind, although most dogs, even when almost totally blind, seem to deal with their diminished sight with little or no problem.

• Ears: Presbycusis is the fancy name for the decline in hearing associated with various types of auditory system dysfunction that accompany aging. It is common in geriatric dogs, and it is a progressive disorder.

• Nose: As dogs age, they begin to lose their acute sense of smell. A dog’s scenting ability is his entryway into his surrounding world; dogs especially rely on their sense of smell to find (and enjoy) food. As a result of the naturally diminishing ability to smell, older dogs may grow increasingly less venturesome and more cautious, and they are likely to lose interest in eating, especially bland foods.

• Hormones: As hormonal systems tend to wane in their strength of output, this ebb of ability affects other systems. One of the most noticeable of these systems is the skin, and older dogs may develop any number of hormonally related skin conditions.

The thyroid, pancreas (especially as related to insulin production for glucose metabolism), and adrenal glands are of particular concern with aging, and they should be routinely monitored in the geriatric dog.

The dramatic decrease in estrogen that is seen in menopausal women oftentimes creates bone thinning as a result of reabsorption of bone calcium. Although we might expect a similar condition to develop in our spayed dogs (or in elderly intact bitches with decreased production of estrogen), it has not been reported as a problem.

• Joints: Older joints are less well oiled, and this lack of lubrication can be painful when the animal moves. In addition, wear and tear of the joints’ surfaces begins to take its toll, and inflammatory changes and/or bony growths may occur.

• Brain: Nerve cells are not especially good at reproducing themselves, and as an animal ages, its amount of brain tissue shrinks. Along with this shrinkage of cellular mass comes a shrinking of cognitive abilities. The aging brain may also develop sclerotic plaques, and the neurons may, as they do with Alzheimer’s, tangle into a web of dead neurons.

Diminished brain function (cognitive dysfunction) may lead to apparent memory loss or disorientation, sleep disturbances (either waking at the wrong time or sleeping unusually deeply), and loss of interest in social activities with the family. (In one study, 32 percent of dogs 11 years old were affected by this syndrome and 100 percent of dogs 16 years of age or older were affected.)

• Urinary System: Age-related dysfunction of the urinary system can cause or contribute to incontinence or inappropriate urination. The underlying cause of the dysfunction may be one of several sources. These include increased volume or frequency (as a result of diminished renal function, the dog may drink more, resulting in increased urinary frequency); discomfort during urination; or decreased control (due to faulty innervation to the bladder or sphincter muscles of the bladder).

Decreased functional capacity of the kidneys themselves can be monitored via periodic urinalysis and blood chemistries. Keep in mind that most of the older tests detected damage only after both kidneys had lost about 60 percent of their functional capacity; newer tests are much more sensitive. Check with your vet.

• Cardiovascular: While decreased func-tionality of the cardiovascular system occurs with some frequency in dogs, it is not typi-cally associated with the atherosclerotic plaques seen in the human animal. Most severe problems related to the aging heart can be detected via an annual (or semi-annual) physical that includes listening to the heart with a stethoscope.

• Lungs: Lung tissues tend to become less elastic as an animal ages, resulting in a diminished functional capacity – and a dog that would rather not exercise to extremes. The lungs are also a common site for the occurrence of tumors that have spread from other areas of the body. Any time your dog is reluctant to exercise or has difficulty breathing or walking long distances, have your vet listen to the lung sounds, and a follow-up chest radiograph may be indicated.

• Liver: The liver is the primary organ of detoxification, and even though a healthy liver has tremendous regenerative powers, a liver that has been exposed to an overload of toxins over the years will eventually wear out. A decline in liver function can be subtle; an annual blood chemistry will help detect early problems.

• Behavior: There are several behavior problems that are prevalent in the geriatric animal, and many of these can be attributed to the diminished ability of other organ systems. With all their senses dulled, many older dogs become “crotchety,” and they would often prefer to be left alone. The disorientation and memory loss associated with cognitive dysfunction may make them seem “spacey” at times, and their sleep irregularities may affect the whole family. In addition, body thermoregulatory mechanisms seem to deteriorate in many dogs, and older animals will not be able to tolerate the same extremes of heat or cold they once could.

Anti-aging basics
Fortunately, there are many things we can do to make older dogs more comfortable and healthy in their senior years.

• Avoid stress. Extremes of heat and cold, hordes of visitors (especially rambunctious kids), changes in routine, or even a new pup may be too stressful for some aged dogs.

• Provide a top-quality diet – preferably a home prepared diet, but certainly one that is highly palatable, contains a high quality and readily digestible protein, and meets the increased needs of the aging animal. You may need to tempt your dog’s appetite with frequent diet changes and/or a top-dressing of herbal spices, which are also an excellent source of antioxidants.

• Supplements may be helpful, especially any of the antioxidant supplements such as vitamins A, C, and E; herbal antioxidants; omega-3 fatty acids; etc. Specific supplements to treat for such problems as cognitive dysfunction, cataracts, arthritis, and inappropriate elimination are available; check with your holistic vet.

• Alternative medicines may be helpful, especially for particular conditions.

For example, I’ve found nothing better for treating arthritic joints than a combination of acupuncture and chiropractic, perhaps with glucosamine, MSM, and Omega-3 fatty acids added to the diet. In my experience, kidney problems seem to respond well to acupuncture, and the herb gingko has been shown to help both memory loss and some of the causes of deafness.

Herbal remedies often are high in antioxidants, and can be selected to target organ systems that are shown to be at risk in the individual. Homeopathic medicines can often be helpful, and they have much less risk of adversely affecting organ systems with age-related diminished capacity.

• Avoid toxins – environmental, dietary, or those related to drugs and vaccines. The older dog’s diminished capacity in many organ systems does not allow for adequate detoxification or elimination of substances that he readily dealt with in his youth.

• Target organs at risk. Use prevalent symptoms and a complete veterinary work-up, including blood chemistries, to diagnose the organ systems that are not functioning properly. Then . . .

• Treat the organ systems holistically. Look at the big picture: the quality of life during the last period of the individual’s lifetime. This “big picture” look may or may not require any intervention, and it certainly requires a long and hard look at any potential intervention that may adversely affect the individual.

• Moderate exercise is a mandatory “medicine” for any and all critters, and for each and every organ system of the body.

• Exercise the mind. Don’t believe the old saw, “You can’t teach an old dog new tricks.” In fact, the more we stimulate a dog’s brain – with new teachings, new places to see and smell, new things to do – the better chance we have to help him maintain normal cognitive function.

• Keep your hands on your dog. A daily massage is magical medicine for the aged animal.

• Stay positive. Maintain a positive outlook on your dog’s prospects and life in general; your dog will pick up your positive vibes. But . . .

• Remain skeptical. No one yet has found the fountain of youth, nor have they come up with a magic anti-aging bullet. Suspect anyone who tries to tell you otherwise.

We are beginning to understand some of the ways the body goes through the process of aging, and come up with ways to enhance the quality of life during old age. While death will eventually catch up to us all, we can help ease the process of getting there, and help aging be a more pleasant reality for our best buddies.

Also With This Article
“Caring For Elderly Dogs”
“Spending the Golden Years with Dogs”
“10 Ways to Make Your Old Dog Comfortable”

-Dr. Randy Kidd earned his DVM degree from Ohio State University and his PhD in Pathology/Clinical Pathology from Kansas State University. A past president of the American Holistic Veterinary Medical Association, he’s author of Dr. Kidd’s Guide to Herbal Dog Care and Dr. Kidd’s Guide to Herbal Cat Care.