Their findings are valuable not only for learning about dogs, she said, 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."
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.
"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."
According to Daniel Promislow, a genetics professor in the Franklin College and co-author of the paper, "when researchers have looked at the effect of reproduction on survival rates in humans, the results have 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."
The authors note that the average life span seen in this study is likely lower than what would be observed in the population of dogs at large. Those observed for the study had been referred to a veterinary teaching hospital and
|Contact: Kate E. Creevy|
University of Georgia