By Emily Anthes
All dogs go to heaven. But a bulldog might find itself headed there years before a border terrier, according to a new study of nearly 600,000 British dogs from more than 150 breeds.
Large breeds and breeds with flattened faces had shorter average life spans than smaller dogs and those with elongated snouts, the researchers found. Female dogs also lived slightly longer than male ones. The results were published in the journal Scientific Reports on Thursday.
There are exceptions to those broad trends, and the findings might not apply to dogs outside Britain, where breeding practices — and gene pools — may be different, the researchers noted.
More research will be needed to determine why some breeds have shorter life spans than others. Some breeds are genetically predisposed to serious health problems, but breed-related differences in behavior, lifestyle, diet, environment or other factors could also play a role in shortening some dogs’ lives, experts said.
“Now that we have identified these populations that are at risk of early death, we can start looking into why that is,” said Kirsten McMillan, an author of the new study and the data manager at Dogs Trust, a dog welfare charity in Britain that led the research. “This provides an opportunity for us to improve the lives of our dogs.”
The study is based on a database of 584,734 British dogs, which the researchers assembled from breed registries, pet insurance companies, veterinary companies and other sources. These types of records, which can be prone to various biases, are not necessarily representative of Britain’s general canine population, the scientists acknowledged.
But Dr. Audrey Ruple, a veterinary epidemiologist at Virginia Tech who was not involved in the new study, said the researchers’ use of so many different data sources was one of the study’s strengths. “I think this is a fantastic approach,” she said.
Most of the dogs were purebred, representing one of 155 breeds; the rest were combined into a single crossbred category. The researchers categorized each breed’s overall body size as small, medium or large and its head shape as flat-faced, medium-proportioned or long-faced.
Across all dogs, the median life span was 12.5 years, the researchers found, but average life span varied “quite spectacularly” among breeds, McMillan said. Lancashire heelers, a breed of petite herding dogs, were canine Methuselahs, living 15.4 years on average. The much larger Caucasian shepherd dogs, though, had an average life span of just 5.4 years.
As a group, small breeds lived 12.7 years on average, compared with 11.9 years for large breeds. This was consistent with prior research on dogs and other mammals, which has generally found that within a given species, smaller individuals tend to outlive larger ones.
Flat-faced breeds, which are also called brachycephalic, lived 11.2 years on average, while medium- and long-faced breeds had average life spans of 12.8 and 12.1 years. Some flat-faced breeds, such as the French bulldog, have become wildly popular. But experts have warned that their extremely short snouts can lead to respiratory problems, heat stroke and other health challenges.
Some of the traits associated with shorter life spans also appeared to compound one another, the researchers found. As a group, small, long-nosed breeds, such as miniature dachshunds and whippets, lived 13.3 years on average — roughly 2 1/2 years longer than large, short-nosed breeds such as boxers and bull mastiffs, which together had an average life expectancy of 10.7 years.
Evolutionary history played a role, too. Closely related breeds had more similar life expectancies.
The researchers also found that purebred dogs, as a group, had average life spans of 12.7 years compared with 12.0 years for crossbred dogs. That survival advantage for purebred dogs contradicts some prior research and could stem from the fact that all crossbred dogs — regardless of size or breed mix — were combined into a single category, scientists said.
But Ruple said she was glad to see results that challenged the conventional wisdom that mixed-breed dogs are always healthier than their purebred counterparts. “I think it is a more complex question than that,” she said. “There are pure breeds of dogs that are generally pretty healthy.”