Dog owners in the U.S. overwhelmingly opt to neuter their pets due to concerns about overpopulation and to make a dog's behavior more manageable. But now a new study out of the University of California at Davis has found that the choice to neuter your dog could be harming its health, according to

The study examined the health records of 759 golden retrievers, including males and females, and found that neutering was correlated with an increased risk in instances of joint disorders and several cancers. Perhaps most surprising, though, is that the study also found that the risk depended upon the age that the dog was neutered. For instance, dogs neutered before the age of 1 saw a 100 percent increase in the the incidence of hip dysplasia, a joint disorder.

"The study results indicate that dog owners and service-dog trainers should carefully consider when to have their male or female dogs neutered," said lead investigator Benjamin Hart.

Hart added that the study's results may differ depending on the breed. Only golden retrievers were examined here, in part to streamline the results to focus on a single breed, but also because golden retrievers offer a large sample size to pool results from due to their popularity. The five disorders (two joint disorders and three cancers) that the research focused on also happen to be common ailments found in golden retrievers: hip dysplasia, cranial cruciate ligament tear, lymphosarcoma, hemangiosarcoma and mast cell tumor.

Although the animal's age when it was neutered affected its risk of disease, all five of the diseases analyzed were recorded at higher rates among neutered dogs compared to non-neutered dogs. So even if a dog owner is careful about when he neuters his pet, there is still a risk involved.

Researchers suggest that the reason why neutering increases the risk of joint diseases and cancers is because the removal of the testes or ovaries interrupts hormone production. The increased occurrence of joint disorders like hip dysplasia in dogs that are neutered at a young age is probably because hormones play a key role in early joint development. Again though, how this affects different breeds of dogs depends on the developmental patterns of each particular breed.

It's also important to keep in mind that some of the disorders analyzed, such as mast cell tumors and hemangiosarcoma, had an increased occurrence among female dogs that were spayed later in life (after a year of age). 

Reseachers hope that more detailed study will aid dog owners in deciding about the best time they should get their pets neutered, if at all, depending on the animal's sex, age and breed.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Does neutering your dog harm its long-term health?
A new study finds that a dog's risk for developing certain cancers and joint diseases increases significantly depending on the age it was neutered.