How Often and How Hard, Not What Kind: Exercise Patterns Predict Cancer in Golden Retrievers

For more than a decade, thousands of Golden Retrievers and their devoted owners have been quietly building one of the most valuable datasets in veterinary medicine. Now, that dataset has yielded a striking and unexpectedly practical insight: when it comes to predicting which dogs will develop cancer, what matters most about exercise is not the type of activity a dog performs, but how often, how fast, and for how long it moves. The finding, published in the journal Veterinary Oncology, represents the first attempt to apply machine learning to the physical activity records of every dog enrolled in the Golden Retriever Lifetime Study, the first prospective longitudinal study ever conducted in veterinary medicine.

The Golden Retriever Lifetime Study, launched in 2012 by the Morris Animal Foundation, was designed to untangle the dietary, genetic, and environmental risk factors behind four major canine cancers: lymphoma, hemangiosarcoma, high-grade mast cell tumors, and osteosarcoma. Golden Retrievers were chosen deliberately. Roughly half of all deaths in the breed are attributed to cancer, according to data from the Veterinary Medical Database, and the breed shows a markedly elevated incidence of hemangiosarcoma and lymphoma. Because privately owned dogs were enrolled young, between six months and two years of age, and followed with annual questionnaires, veterinary examinations, and biological sampling, the study captures lifestyle exposures years before any diagnosis is made.

In the new analysis, Dennis Ronzani of Ross University School of Veterinary Medicine and Sarah E. Hooper of Arkansas State University examined the activity and lifestyle questionnaire responses of 3,044 purebred Golden Retrievers across the first seven years of the study. During that window, 277 dogs were diagnosed with cancer, with a median age at diagnosis of 6.1 years. The researchers asked a deceptively simple question: could the exercise habits reported by owners, on their own, distinguish dogs that would develop cancer from those that would not?

Answering that question required overcoming a statistical obstacle that has long discouraged researchers from mining longitudinal cohort data. Standard machine learning algorithms assume that every data point is independently sampled, an assumption shattered by repeated annual measurements of the same dog. Classical models, meanwhile, struggle when the number of observations is smaller than the number of predictors. The team turned to a hybrid method called the BiMM forest, developed by Speiser and colleagues, which combines a generalized linear mixed model with a random forest algorithm. This architecture is specifically built to handle clustered, high-dimensional data with nonlinear relationships and interactions between predictors, making it well suited to serial owner reports spanning multiple years.

The researchers built two models. The first used only questions asked consistently from year zero through year seven; the second incorporated additional questions about the pace and duration of exercise that the Morris Animal Foundation added to the questionnaire starting in year three. The difference in performance was dramatic. The years zero through seven model achieved an overall accuracy of just 68.2 percent, while the years three through seven model reached 80.7 percent accuracy, an F1 score of 74.9 percent, and a fair area under the receiver operating characteristic curve of 0.763. The lesson was clear: knowing how briskly and how long a dog exercises carries far more predictive signal than knowing only which activities it performs.

Ranking the predictors by their mean decrease in Gini importance, the team found that the top variables were year in study, exercise frequency, exercise pace, exercise duration, and the frequency of swimming in both warm and cold weather, followed by the owner-reported overall activity level. Four of the ten most important predictors related directly to the frequency and duration of aerobic activity. Perhaps most surprising, the specific type of exercise and the surface on which it took place ranked low in importance. It was the rhythm and intensity of movement, not the movement itself, that carried the strongest association with cancer status.

The data also revealed a poignant behavioral shift after diagnosis. Owners of dogs diagnosed with cancer reported an 8 to 10 percent increase in exercise frequency in the years following the diagnosis, and a 15.6 to 68.88 percent increase in cold weather swimming, while warm weather swimming declined by 2.0 to 13.9 percent. At the same time, exercise pace and duration fell, with dogs diagnosed in year four showing a 7.8 percent reduction in duration and overall activity levels declining by as much as 15.5 percent. The authors suggest this pattern may reflect veterinary recommendations or owner research into the benefits of exercise for canine cancer patients, mirroring the well-documented phenomenon in which roughly three out of four human cancer survivors meet physical activity guidelines after diagnosis.

The findings resonate strongly with human oncology research. Moderate-to-vigorous physical activity is firmly associated with reduced risk of colon, kidney, liver, and mammary cancers in people, and has been shown to delay cancer onset even in women genetically predisposed to breast cancer. Laboratory studies add mechanistic weight: moderate-intensity exercise inhibits cancer cell proliferation and induces apoptosis in animal models, whereas strenuous activity can, in some contexts, promote tumor growth. Notably, most Golden Retrievers in the study exercised at a brisk walking pace for 10 to 60 minutes per session, which qualifies as moderate intensity under the Physical Activity Guidelines for Americans, yet the total weekly volume often fell short of the 150 to 300 minutes recommended for humans, echoing the finding that three quarters of the US population also fails to meet those guidelines.

The swimming data carry their own intriguing, and cautionary, dimension. Dogs diagnosed with cancer swam slightly more often in cold weather before diagnosis, and cold weather swimming rose sharply afterward, possibly reflecting the growing popularity of aquatic therapy and underwater treadmills for canine rehabilitation. But water quality introduces a potential confound. The US Environmental Protection Agency reports that more than 13 million acres of lakes and ponds are impaired by pollution, and epidemiological studies in humans have linked disinfection by-products such as trihalomethanes in chlorinated pools to increased cancer risk. One prior study even found that dogs with urothelial cell carcinoma were more likely to have swum in pools than cancer-free dogs, a connection the authors say warrants closer investigation.

The study has limitations that its authors acknowledge candidly. Because a data embargo restricted the analysis to the first seven years, many dogs had not yet reached the typical age of cancer diagnosis, and fewer than 10 percent of the cohort had a neoplastic diagnosis, too few to build models for individual cancer types. All cancers were therefore grouped together, and missing body condition score data, available for only some dogs and years, prevented the team from accounting for obesity, itself a known risk factor for certain canine cancers. Still, the authors argue that the results point toward a future in which veterinarians can offer evidence-based exercise guidance for dogs, focused on frequency, duration, and pace rather than activity type, and in which cumulative lifestyle exposures, shaped by owner behavior and environment, take their rightful place in canine cancer risk assessment. As more years of Golden Retriever Lifetime Study data become available, the same machine learning approach may reveal whether these patterns hold for specific tumors, and whether adjusting a dog’s exercise routine could genuinely shift its cancer risk.

Subject of Research: Physical activity patterns as predictors of cancer development in Golden Retrievers

Article Title: Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type

Article References: Ronzani, D., & Hooper, S. E. (2025). Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type. Veterinary Oncology, 2(1), Article 11. https://doi.org/10.1186/s44356-025-00024-5

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00024-5

Keywords: Golden Retriever, canine cancer, machine learning, physical activity, Golden Retriever Lifetime Study, veterinary oncology, BiMM forest, exercise frequency, exercise intensity, swimming, cancer risk factors, longitudinal study