A new study published today is diving deep into how a dog’s size can affect their health. The study found evidence that larger dogs tend to have a higher risk of many health problems and generally shorter lifespans, while also showing that smaller dog breeds can have their own unique health risks as well.
The research is the latest to emerge from the Dog Aging Project, an initiative billed as the most ambitious of its kind in the world. The project intends to track companion dogs over a 10-year span to better understand the factors that can help dogs—and humans—live longer, healthier lives. Volunteer pet owners are asked to complete annual questionnaires about their dogs’ health, while some will also provide veterinary records and test samples for smaller studies.
For this study, published Wednesday in PLOS-One, the researchers focused specifically on dog size, looking for potential associations between size and a large list of health conditions. Ultimately, they looked at data from over 27,000 dogs across 238 breeds.
Overall, they found that larger dogs were more likely to have many different diagnosed health problems than smaller ones. These problems included cancer, diseases of the ear, nose and throat, neurological conditions, and gastrointestinal issues. Smaller dogs, however, were more likely to develop eye, cardiac, and liver problems, as well as respiratory disease. The risk of kidney and urinary problems appeared to be the same for big and small dogs. These patterns held up even after the researchers tried to account for factors like sex, where the dogs lived, and whether they were purebreds or mixed breeds. But both age and size seemed to influence a dog’s risk of developing many health conditions over the course of their lifetime.
These kinds of studies can’t directly prove a cause-and-effect link between dog size and health—they can only establish a correlation. But coupled with other evidence, the findings do strengthen the idea that larger dogs do tend to live shorter lives than smaller dogs, the researchers say. The findings disclosed in the new paper may also lead to some new areas of interest for future studies.
Contrary to some past research, for instance, the authors found that larger dogs were more likely to have hormone-related problems, particularly hypothyroidism (an underactive thyroid, resulting in weight gain, lethargy, skin problems, among other conditions). If this increased risk is genuine, the authors note, then a greater recognition of it could go a long way in helping big dogs stay healthier, especially since treatments for hypothyroidism are relatively easy and inexpensive to provide.
“These results provide insights into the disease categories that may contribute to reduced lifespan in larger dogs and suggest multiple further avenues for further exploration,” the researchers wrote.
The Dog Aging Project is still ongoing, and the lessons we learn from it will only help scientists and dog owners find the best ways to keep their pooches healthy and living long fruitful lives.