Canine mortality: 20-year study of dog breeds diseases, death rates

ATHENS, GA. — Large breeds don't just have shorter life spans than smaller dogs—they are also more likely to die of musculoskeletal and gastrointenstinal diseases and cancer. Smaller breeds live longer on average but are more prone to die of metabolic diseases, according to a new 20-year retrospective on canine mortality trends by researchers at the University of Georgia.

The study breaks down a number of causes of death according to age, breed and size. Researchers, led by Dr. Jamie Fleming of Lakeshore Veterinary Specialists, used records from the Veterinary Medical Database (VMDB), established in 1964 by the National Cancer Institute. Data was culled from records of 74,556 canine deaths from 1984 to 2004, according the study.

Toy breeds like Chihuahuas (19 percent of deaths) are known to have high rates of cardiovascular disease, but Dr. Kate Creevy, assistant professor in the University of Georgia (UGA) College of Veterinary Medicine, and Daniel Promislow, a genetics professor in the UGA Franklin College of Arts and Sciences, say Fox Terriers trailed Chihuahuas by just 3 percent. Additionally, Golden Retrievers and Boxers have been noted to suffer from cancer at a high rate (50 and 47 percent of deaths, respectively), but the more rare breed Bouvier des Flandres died of cancer slightly more frequently than the Boxer.

"With rare breeds, an individual veterinarian may not see enough cases to be able to develop an opinion on whether the breed has a high incidence of conditions such as cancer," Creevy says. "But if you analyze records that have been compiled over 20 years, you can detect patterns that you wouldn't notice otherwise."

Overall, Creevy and Promislow found that younger dogs most often died of gastrointestinal or infectious diseases, trauma and congenital abnormalities, while causes of death in older dogs shifted to neurologic and neoplastic causes.

Also, while larger dogs have a shorter life span than smaller breeds, the study notes that larger individuals within various breeds are more likely to live longer.

More than 80 breeds were represented in the study, and certain trends were revealed by breed type. Gastrointestinal diseases were most often listed as the cause of death in Great Danes, Akitas, Gordon Setters, Shar peis and Weimaraners. Newfoundlands, Maltese, Chihuahuas, Doberman Pinschers and Fox Terriers succumbed most frequently to cardiovascular causes. Neurologic diseases were the most common causes of death in Dachshunds, Miniature Dachshunds, Dutch Pugs, Miniature Pinschers and Boston Terriers. Musculoskeletal diseases were the top causes of death for Saint Bernards, Great Pyrenees, Irish Wolfhounds, Great Danes and Greyhounds.

While not a top cause of death, urogenital disease was commonly found in Scottish Terriers, Airedale Terriers, Dalmatians, Norwegian Elkhounds and Standard Schnauzers. Respiratory diseases were listed as causes of death most often in Bulldogs, Borzoi, Yorkshire Terriers, Afghan Hounds and Treeing Walker Coonhounds, according to the study. Newfoundlands, Bulldogs, Yorkshire Terriers, Akita and Maltese had the highest incidence of deaths of congenital diseases.

Considering their findings on causes of death, the study authors note that further research into the disproportionate rates of musculoskeletal and neoplastic disorders in large-breed dogs would be useful in understanding their shorter life spans.

The full study can be found in the March/April 2011 issue of the Journal of Veterinary Internal Medicine.