Sterilized Dogs Live Significantly Longer
April 18, 2013

Getting Your Dog ‘Fixed’ Could Add Years To Its Life

Lee Rannals for - Your Universe Online

It turns out, Bob Barker's advice to "have your pet spayed or neutered" wasn't just a tip for controlling the stray animal population. New research from the University of Georgia suggests that spaying or neutering your dog adds extra time to their life and reduces the risk of several specific causes of death.

For the study, the team examined 40,139 death records from the Veterinary Medical Database spanning a 10-year period. The researchers found that the average age at death for dogs that have not been neutered or spayed was 7.9 years compared to 9.4 years for sterilized dogs.

"There is a long tradition of research into the cost of reproduction, and what has been shown across species is if you reproduce, you don't live as long," said Dr. Kate Creevy, an assistant professor of internal medicine at the UG College of Veterinary Medicine.

"The question that raises is why would you die younger if you have offspring?"

The team measured the costs of reproduction in terms of the actual causes of death, and found that the causes of death differed between sterilized and intact dogs. Dogs that underwent a spay or neuter surgery were more likely to die from cancer or autoimmune disease while non-sterilized canines were more likely to die from infectious disease or trauma.

"Intact dogs are still dying from cancer; it is just a more common cause of death for those that are sterilized," said Jessica Hoffman, a UGA doctoral candidate in the Franklin College of Arts of Sciences who co-authored the study.

Creevy says that if you plan on sterilizing your dog, you should be aware of possible risks of immune-related diseases and cancer. She said the findings are valuable not only for learning about dogs but also for studying reproductive effects in humans as well.

"There is no other species where we can even begin to study cause of death as closely as we do with dogs," Creevy said. "They model our own disease risk because they live in our homes, sleep in our beds and eat our food. All of the things that impact us and our health impact them."

She suggests that some of the reproductive hormones could suppress the immune system, which would explain why there is an increased risk of infection among dogs that have been sterilized.

"There are a few studies of people who are sterilized, specifically among men who are castrated for cultural or medical reasons," Creevy said. "Interestingly, there was a difference in their life spans too, and the castrated men tended to live longer. The men in that study who were not sterilized also got more infections, supporting the idea that there is a physiological reason for this."

Daniel Promislow, a genetics professor in the Franklin College and co-author of the paper published in the online journal PLOS ONE said the past study results varied from one study to the next.

"Our findings suggest that we might get a clearer sense of potential costs of reproduction if we focus on how reproduction affects actual causes of mortality rather than its effect on life span," Promislow said.

The team said the average life span in the study is likely lower than what it would be observed in the population of dogs at large because the canines in the study represented a population of sick animals.

"The overall average life span is likely shorter than what we would observe in private practice, because these were dogs seen at teaching hospitals, but the difference in life span between sterilized and intact is real," Creevy said. "The proportionate effects on causes of death are translatable to the global dog population, and it will be interesting to see if explanations for these effects can be found in future studies."