New research from the University of Georgia suggests that neutering procedures could add to the length of a dog’s life and alter the risk of specific causes of death.
Looking at a sample of 40,139 death records from the Veterinary Medical Database from 1984-2004, researchers determined the average age at death for intact dogs—dogs that had not been spayed or neutered—was 7.9 years versus 9.4 years for sterilized dogs.
These figures may seem low considering how many pets live much longer, but the researchers noted that the life spans would be lower than those seen more widely because their sample was taken from dogs seen at teaching hospitals (so other things would have been going on and the study population would have had more sick animals).
The researchers stand behind their results – that the difference between neutered and intact is real.
Dr. Kate Creevy, an assistant professor of internal medicine at the College of Veterinary Medicine. “The question that raises is why would you die younger if you have offspring?”
For the first time, researchers have been able to measure costs of reproduction in terms of the actual causes of death, finding that the causes of death differed between sterilized and intact dogs. Dogs who had undergone a gonadectomy (a spay or castration) were more likely to die from cancer or autoimmune diseases. Those in the sample who still had functional reproduction systems at death were more likely to die from infectious disease and 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.
Some of the reproductive hormones, particularly progesterone and testosterone, she said, could suppress the immune system, explaining why there is an increased risk of infection among dogs that have been sterilized.
The full journal article, published in PLoS One, can be viewed here.