Sterilised dogs live longer: study

Dog owners, please note! Having your pet spayed or neutered could increase its life span, a new study has claimed.
Researchers from the University of Georgia in US looked at a sample of 40,139 death records from the Veterinary Medical Database from 1984 to 2004.
They 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 sterilised 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 College of Veterinary Medicine.

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 eventual cause of death.
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 sterilised 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 sterilised," said Jessica Hoffman, a UGA doctoral candidate in the Franklin College of Arts of Sciences who co-authored the study.
"At the level of the individual dog owner, our study tells pet owners that, overall, sterilised dogs will live longer, which is good to know," Creevy said.
"Also, if you are going to sterilise 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," Creevy added.

The authors noted that the average life span seen in this study is likely lower than what would be observed in the population of dogs at large.
The dogs observed for the study had been referred to a veterinary teaching hospital and represent a population of sick animals.
The study was published in journal PLOS ONE.