From time of conception, we all start dying on the installment plan. We age. We age irreversibly for the most part, and to each of us, is allotted only so much time on the biological clock for various life functions and various life stages. This aging process is true for our dogs also, only it happens much faster.

This five part series will address the physical and psychological aspects of aging to include an overview of the aging process, common maladies, normal deterioration and loss of function commensurate with old age, reduced immune response, managing chronic conditions, last days, and a need to make provisions for your dogs in case you are no longer able to care for them, or do not survive them.

Life extension is still beyond our technical capabilities, though the search for the “fountain of youth” has been ongoing since very early times. Having your dog live to a “ripe old age” is more a function of avoiding accidents and disease, thus achieving the genetic life span potential of the individual dog. We will cover what you can do to extend the length of time your dog stays active and healthy.

At the outset, regardless of what you may read in the popular press, tabloids or at health food stores, the only procedure found to extend maximum life span in experiments with dogs is caloric restriction in otherwise sound diets There are fortunately nutritional, medical and lifestyle steps that can be taken to maximize the period of general good health and activity. We will cover those in detail in subsequent articles.

The aging process is a complex series of challenges met and challenges not so well met. The overall toll of life events, such as pregnancies, illness and trauma is cumulative. We know this from our own experience — the sprain of a joint as a child makes that joint more prone to arthritis in old age. The central concept to body functioning is homeostasis.

Homeostasis

Homeostasis is that dynamic process whereby the various body systems function to maintain internal stability which keeps the body operating, repaired and protected. Aging is the net effect of negative changes in physiology (loss of homeostasis) that occur over time, from conception to inevitable death. Older dogs are less able to handle threats to their body systems than are dogs in their prime. Old dogs, especially males, are particularly susceptible to the harmful effects of free radicals and lipid peroxidation. Body systems can be categorized several ways and further broken down into subsystems. For the purpose of this series we will discuss aging within the framework of the following classification scheme based on function and the systems that support those functions.

The major body functions are: regulatory, nutritional, excretory, distributive, protective and reproductive. We define anything that negatively influences this dynamic and generally robust balance as stress. Thus stress beyond the self-compensating properties of the body systems results in a loss of homeostasis. Generally, there is a balance between stimulus, which excites the body systems to function, and stress, which may overload them. Thus while exercise is good for the dog, dogs used as motive power in medieval times often died early deaths from “overwork,” i.e., stress.iii Stress applied to bones is necessary to keep them well-calcified.iv (Susan–should we say, “well-ossified” or “well-mineralized’? And do we need a citation for this that bones need to be mechanically stressed as a part of the calcium balance?)

Life Span

Each breed of dogs has its own characteristic maximum life span, i.e. that period of time during which homeostasis is maintained. Yet within each breed, there are lines that live longer or shorter than the average. Thus in determining the dog’s “physiological age,” it is important to take into account not only the breed, but also the line. See Table 1 for a listing of median life spans for a representative sampling of breeds. With many Great Danes and Irish Wolfhounds, for instance, geriatric at five years and dead at seven years, the aging process is relatively rapid. Contrast this with one of the small terriers, or miniature or standard poodles, which live more than twice as long. Numerous studies have attempted to quantify the lifespan of various breeds, but more often than not, external factors such as nutrition, disease, environment, quality of data and statistical sampling techniques have interfered to make it difficult to say a great deal with much certainty. Previous work, comparing the relationship between human and dog ages, recognized that it was not a constant (1:7 ratio) over the dog’s life span.

We present, for your review, Patronek et al’s refinement which takes into account the non-linear aspects of canine aging. Figure 2 graphs chronological dog ages of mixed breed dogs in five different weight categories against human equivalents. Figure 1 median life spans may be inputed into the Figure 2 equation to determine breed specific human age equivalents. A study is currently ongoing at the Michigan State University to develop a longevity and mortality database of purebred dogs.v To participate in this study and to submit data on your own dogs, go to “http://35.8.210.35/Dog_Study/details.htm” on the internet. An independent study is being conducted by Dr. John Armstrong, University of Ottawa, using the CANGEN-L special interest list. For more information, go to the Diversity Project .

Figure 3 – Geriatric Screening Guidelines

Systems

As your dog ages his joints will age as well and you will begin to worry about arthritis and your dog. There are signs that you can look out for in your dog as he ages that will help you to tell whether your dog is developing arthritis.

Things to look out for in your aging dog:

Your dog seems uncomfortable when squatting to use the bathroom

Your dog bites or gnaws at his joints

Your dog has trouble jumping up on the furniture or in to the car and did not have this trouble previously

Your dog needs to rest more often than he did previously

Your dog can no longer climb the stairs as he used to

Your dog doesn’t respond to exercise as he once did or he tires more quickly

Your dog seems stiff when getting up from rest

Your dog limps or has problems walking

Your dog limps more or has more trouble with stiff joints in cold weather

Your dog would rather lie down than sit or stand

Your dog seems more depressed or uncomfortable than usual and looses interest in food

Your dog seems uncomfortable when touched in certain areas that seem to be giving him trouble.

If you notice any of these signs in your dog you should take him to your vet immediately to find a treatment plan that is customized to your dog. You should also be aware that some of these signs can also signal other health problems, such as a loss of interest in food, and should be evaluated by your vet as soon as possible.