Spayed Dogs Live Longer: Study

Sterilization not only helps control the dog population, but also extends lives of the pets, according to a new study based on more than 40,000 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. The question that raises is why would you die younger if you have offspring?" said Dr. Kate Creevy, an assistant professor of internal medicine at the College of Veterinary Medicine.

The data for the study came from the Veterinary Medical Database from 1984-2004. Researchers found that spayed or neutered dogs had an average age of 9.2 years when compared with 7.2 years for an intact dog.

Researchers from University of Georgia also found that dogs that were spayed were more likely to die from cancer or autoimmune disease, while dogs that had a functional reproduction system died due to infectious disease or trauma.

Now, there have been studies on reproduction and life span, but they have been mostly conducted on mice, worms or fruit flies. The latest study even accounts for the various causes that lead to the death of dogs that are either neutered or intact.

"At the level of the individual dog owner, our study tells pet owners that, overall, sterilized dogs will live longer, which is good to know. Also, if you are going to sterilize your dog, you should be aware of possible risks of immune-mediated diseases and cancer; and if you are going to keep him or her intact, you need to keep your eye out for trauma and infection," said Creevy in a news release.

Creevy added that learning about how reproduction affects the life span of dogs can help researchers understand the link between reproduction and life span in humans, as dogs have diseases similar to humans. In addition, as pets, dogs share our homes, food and microbes, showing that they have the same kinds of lifestyle-related conditions.

Also, since the study looks at specific causes of death and reproduction, it could give a clearer picture of how reproduction affects health. Previous studies on humans have failed to draw a conclusion as they focus on the entire life span and not specific causes, researchers said.

"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," said Daniel Promislow,  who is a  genetics professor in the Franklin College and co-author of the paper.

The study is published in the journal PLOS One.