Big dogs versus small dogs: Which sizes face higher risks of which diseases?

A study of more than 25,000 U.S. dogs and 238 breeds has linked dog size to varying patterns of risk for health conditions over the course of a dog’s lifespan. Yunbi Nam of the University of Washington, U.S., and colleagues present these findings in the open-access journal PLOS ONE on January 17.

On average, smaller dogs tend to live longer than larger dogs. Evidence suggests that larger dogs do not tend to have more health conditions, but that dogs of different sizes may face different levels of risk for different conditions. However, more research is needed to clarify links between dog age, size, and disease prevalence.

To deepen understanding, Nam and colleagues analyzed survey data on 27,541 dogs representing 238 breeds, as reported by dog owners participating in the ongoing Dog Aging Project.

Overall, larger dogs in the study were more likely to have faced certain types of health conditions at some point in their lives, including cancer, bone-related disease, gastrointestinal problems, ear/nose/throat issues, neurological and endocrine conditions, and infectious diseases. Meanwhile, smaller dogs were more likely to have experienced ocular, cardiac, liver/pancreas and respiratory diseases. History of kidney/urinary disease did not differ significantly for larger versus smaller dogs.

For many types of conditions—including cancer, ocular, cardiac, orthopedic, and ear/nose/throat conditions—different dog sizes were associated with differing patterns of risk over the course of a dog’s lifespan.

The results held up even after the researchers statistically accounted for the dogs’ sex, where they lived, and whether they were purebred or mixed-breed.

The researchers note that this study does not confirm any causal relationship between dog size, age, and disease. Still, the findings could help lead to deeper understanding of the types of conditions that may underlie the lower lifespan of larger dogs. For instance, within the disease categories explored in this study, future research could home in on age and size patterns associated with specific conditions.

The authors add: “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.”

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0295840

Citation: Nam Y, White M, Karlsson EK, Creevy KE, Promislow DEL, McClelland RL, et al. (2024) Dog size and patterns of disease history across the canine age spectrum: Results from the Dog Aging Project. PLoS ONE 19(1): e0295840. https://doi.org/10.1371/journal.pone.0295840

Author Countries: USA

Funding: This research is based on publicly available data collected by the Dog Aging Project, which is supported by U19 grant AG057377 from the National Institute on Aging, a part of the National Institutes of Health, and by additional grants and private donations. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.