Mortality in North American Dogs from 1984 to 2004: An Investigation into Age‐, Size‐, and Breed‐Related Causes of Death

Abstract

Background: Anecdotal beliefs and limited research suggest variable patterns of mortality in age, size, and breed cohorts of dogs. Detailed knowledge of mortality patterns would facilitate development of tailored health-maintenance practices and contribute to the understanding of the genetic basis of disease.Hypothesis/Objectives: To describe breed-specific causes of death in all instances of canine mortality recorded in the Veterinary Medical Database (VMDB) a between 1984 and 2004. We hypothesized that causes of death, categorized by organ system (OS) or pathophysiologic process (PP), would segregate by age, body mass, and breed.Animals: 74,556 dogs from the VMDB for which death was the outcome of the recorded hospital visit. Methods: Retrospective study. Causes of death from abstracted VMDB medical records were categorized by OS and PP and analyzed by age, breed, and breed-standard mass of dog.Results: Causes of death, categorized by OS or PP, segregated by age, breed, and breed-standard mass. Young dogs died more commonly of gastrointestinal and infectious causes whereas older dogs died of neurologic and neoplastic causes. Increasing age was associated with an increasing risk of death because of cardiovascular, endocrine, and urogenital causes, but not because of hematopoietic 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.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.

The companion dog as a model for human aging and mortality

“…While large differences were seen in proportions of respiratory, gastrointestinal, and urogenital causes of death between humans and dogs, the proportion of neoplastic deaths is nearly identical between the two species (25.3% in humans; 27.4% in dogs; Figure 2c), although cancer risk is generally greater in large‐breed than small‐breed dogs (Fleming et al., 2011). Despite the similarity in risk of death due to neoplasia among humans and canines, the types of cancer seen in each species are only marginally correlated (Spearman rank ρ = 0.661, df  = 7, p  = .053).…”

“…Finally, our canine analysis makes the assumption that all dogs are drawn from the same pool and does not look at the effects of breed and size variation. Previous research has shown that even within a size class, breeds can differ in their multimorbidity (Jin et al., 2016) and mortality patterns (Fleming et al., 2011). Taken together, these limitations point to the need for more detailed data from canines representing the full diversity of ages, breeds, comorbidities, and environments.…”

“…These causes of death were then assigned to a specific pathophysiological process (PP) and organ system (OS) as described previously in Fleming et al. (2011), such that each individual had both a process and system classification of death. Pathophysiological process describes the mechanism leading to the disease and includes congenital, degenerative, infectious, inflammatory (encompassing immune‐mediated), metabolic, neoplastic, toxic, traumatic, and vascular.…”

“…Data obtained included all diagnoses recorded by the attending veterinarians at the time of death for all dogs whose death was documented in the VMDB between 1984 and 2004 ( N  = 73,835 dogs; mean number of diagnoses = 2.97; range of 1–32). For dogs with multiple diagnoses, a single cause of death, including process and system, has been assigned previously (Fleming et al., 2011). Age at death in the VMDB was grouped into bins.…”

“…Thanks in large part to this history of intense breeding for specific morphological and behavioral traits, dogs are the most phenotypically diverse mammalian species on the planet. This diversity is found not only in morphology and behavior, but also in life‐history traits, where across breeds, dogs exhibit an almost twofold difference in average longevity (Bonnett & Egenvall, 2010; Fleming, Creevy & Promislow, 2011), and enormous variation in risk of specific diseases (Fleming et al., 2011). In addition, companion dogs live in diverse environments and often in close proximity with their owners.…”