Ever wondered why our pets die? I do. But not only do I approach it emotionally the same way you might, looking my beloved pets deep in the eyes wondering when they'll leave me behind, I also have a way of geeking out on the mortality stats the veterinary literature occasionally offers. But then, you'd expect nothing less from me, right?
In a retrospective study of almost 75,000 dogs collected from a national veterinary database and published in the Journal of Veterinary Internal Medicine's March/April edition (Mortality in North American Dogs from 1984 to 2004: An Investigation into Age-, Size-, and Breed-Related Causes of Death), the answers rushed onto the page in a flurry of cold hard facts.
Categorized by organ system or pathophysiologic process, then segregated by age, breed, and breed-standard mass, the causes of death were reported as following:
Young dogs died more commonly of gastrointestinal and infectious causes whereas older dogs died of neurologic and neoplastic (cancer) causes. Increasing age was associated with an increasing risk of death because of cardiovascular, endocrine, and urogenital causes, but not because of hematopoietic (blood-related) or musculoskeletal causes. Dogs of larger breeds died more commonly of musculoskeletal and gastrointestinal causes whereas dogs of smaller breeds died more commonly of endocrine causes.
All of which fits mostly with the prevailing veterinary wisdom: Young dogs die of eating stupid stuff and getting random infections while older dogs die of cancer. Meanwhile, smaller breeds are more likely to die of more complex endocrine (hormonal) issues like Cushing's and diabetes while bigger ones succumb more often to the results of things like osteoarthritis and bloat. And yeah, advancing age is correlated with increased risk of mortality due to heart disease, endocrine dysfunction, renal failure, pyometras and prostatic disease. Makes sense.
Of all the stats, I guess the one thing that stands out is that older dogs die of neurologic disease and cancer. Of course, cancer, I get. But why neurologic disease in particular? That, to me, is an eye-opener. Just as for humans, it seems the issue of cognitive dysfunction (doggie dementia) and other forms of neurological decline deserve more consideration than we're currently affording them.
But that's, after all, why studies like these deserve so much of our dedicated geekiness. As the study's authors sagely noted in their section "Conclusions and Clinical Importance":
Not all causes of death contribute equally to mortality within age, size, or breed cohorts. Documented patterns now provide multiple targets for clinical research and intervention.
Now, if only we could get the same kind of study done for our cats...
Dr. Patty Khuly