Multiple Chronic Diseases Double Dogs' Mortality Risk
A study of over 50,000 dogs finds that having five or more chronic conditions more than doubles the annual mortality risk, regardless of age or size
Dogs with five or more chronic diseases are more than twice as likely to die in a given year than dogs with just one condition. This finding comes from a Texas A&M-led analysis of health data from more than 50,000 dogs enrolled in the Dog Aging Project.
According to the research, chronic diseases in dogs do not simply add up independently as they age. Instead, certain combinations of illnesses interact, creating a compounded effect on survival that is greater than the sum of individual conditions. This pattern, known as multimorbidity, is also observed in human medicine.
"Multimorbidity refers to the fact that individuals often become ill with more than one chronic disease at the same time," said Dr. Kate E. Creevy, chief veterinary officer for the Dog Aging Project and a professor at Texas A&M College of Veterinary Medicine & Biomedical Sciences. She noted that in people, having multiple conditions is often more damaging to health and survival than simply adding the effects of two different diseases.
How Diseases Compound Each Other
Researchers compared the health histories of dogs that died during the study with those still living, adjusting for factors like age. They found that chronic conditions tend to cluster and interact. For example, osteoarthritis can reduce a dog's activity, leading to weight gain, which then worsens the osteoarthritis.
Cancer and osteoarthritis were among the disease combinations linked to shorter lifespans. Dental disease frequently occurred alongside other chronic illnesses, and hearing loss was common in dogs with multiple diagnoses. The study authors noted that excess body weight plays a dual role, acting as both a contributor to and a consequence of chronic disease.
"Cancer can affect multiple body systems as it spreads," Creevy explained. "Similarly, osteoarthritis can interfere with the activities of daily living."
Quantifying the Mortality Risk
The study specifically examined the likelihood of death within a single year. "We are all eventually going to die, but this analysis asked the question: for any given year of life, how likely is the dog to die this year?" Creevy said. The data showed the impact was dramatic.
For veterinarians, the findings highlight the importance of considering a dog's full spectrum of health issues together, rather than treating each diagnosis in isolation. Identifying which disease combinations carry the greatest added risk could eventually help clinicians and owners prioritize care. This shows the value of preventive measures like weight management, regular activity, and maintaining dental health.
A Model for Human Aging Research
Dogs offer a compressed model for studying aging. With typical lifespans of 10 to 12 years, researchers can observe an entire aging trajectory in about a decade. Similar longitudinal studies in humans can require following participants for 70 years or more, which is part of why the Dog Aging Project has drawn interest as a translational model.
"The reason we can learn this is because so many dedicated volunteer owners have shared their data with the Dog Aging Project," Creevy stated. Their participation made the research possible.
The study was funded by the National Institute on Aging, part of the National Institutes of Health, along with the Glenn Foundation for Medical Research and the WoodNext Foundation. The authors reported no competing interests.
