Sterilized dogs tend to live longer.

• Position: Veterinary Medicine

Many dog owners have their pets spayed or neutered to help control the animal population, but there is another reason to do so: research from the University of Georgia, Athens, suggests the procedure could add to the length of the animals' lives and alter the risk of specific causes of death.

Looking at records from the Veterinary Medical Database, researchers determined the average age at death for intact dogs--dogs that have not been spayed or neutered--is 7.9 years versus 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," says Kate Creevy, assistant professor of internal medicine at the College of Veterinary Medicine. "The question that raises is: why would you die at a younger age if you have offspring?"

Historically, studies on the effects of reproduction on life span have been done in model systems like mice, nematode worms, and fruit flies, where it is difficult to figure out the eventual cause of death. Now, however, for the first time, researchers have been able to measure costs of reproduction in terms of the actual causes of death, finding that they differ between sterilized and intact dogs. Dogs who have undergone a gonadectomy (a spay or castration) are more likely to die from cancer or autoimmune diseases* Those who still have functional reproduction systems at death are more likely to die from infectious disease or trauma.

The findings are valuable not only for...