More research on health impacts of spay/neuter -- where should we go from here?

Last week, more research came out about the health impacts of Spay/Neuter.

The newest paper specifically studies Vizslas -- and the health impacts of spay/neuter, and particularly juvenile spay/neuter on this breed of dogs.

You can read the paper in its entirety here, or the Reader's Digest Version with great commentary here. In a nutshell, the paper showed the following correlations:

-- 3.5x higher incidences of Mast Cell cancer in male & female dogs, regardless of age of neuter.

-- 9x greater incidence of Hamangiosarcoma in neutered females, regardless of age of dog at the time of neuter.

- 4.3x higher incidence in Lymphoma in both neutered males and females, indpendent of age at the time of neuter.

- 6.5x higher incidence of all cancers combined in neutered femal3, 3.6x higher incidence of all cancers in neutered males. Typically, the younger the age at which the dog was altered, the young the age at which the dog was diagnosed with cancer.

Also, the study notes that dogs altered before the age of 6 months had a higher-likelihood of developing a variety of behavioral issues including: separation anxiety, fear of noises, timidity and fear biting.  Altering after 6 months did not appear to create increased risk.

This study adds to the growing list of research on the negative health impacts of spay/neuter in large-breed dogs. The studies have specifically found similar results plus increased incidence of hip dysplasia and Cranial Cruciate Ligament Tears in Golden Retrievers, and osteosarcoma (bone cancer) in Rottweilers.  It also follows similar issues found in previous behavioral studies on the impacts of spay/neuter.

The results have been very consistent, and show that not only is spay/neuter more likely to cause negative health impacts long-term, but that juvenile spay/neuter (before 6 months) heightens the risk.

When Science gets in the way

For several decades, rescues and shelters have been reliant on spay/neuter to decrease the number of unwanted pets as a way of controlling animal populations, and thus the number of animals that end up in animals shelters. By decreasing total populations, the goal is to minimize the number of animals killed in shelters. 

However, if we are to really consider ourselves "animal welfare" professionals, we need to understand what science is telling us and to consider the trade-offs of the short-term and long-term impacts on our decisions on the pets we are responsible for.

Unfortuantely, in this case, it appears that the long-term health impact of spay neuter, particularly juvenile spay/neuter, is at odds with the short term goal of slowing pet population growth and minimizing the number of animals killed in our shelters every year. 

The two are seemingly at odds with each other. Certainly I've read the arguments that in spite of the potential health impacts of spay/neuter, the greater good of decreasing the number of pets killed at very young ages in shelters outweighs the pet-longevity issues that may exist by spaying/neutering early. I can certainly see this point, and in many cases completely agree. 

However, just because that is the case today, doesn't mean that we have to accept the status quo as the only solution and not be actively seeking out more viable alternatives. It seems clear that there is room for some middle ground here -- and I think it's up to the animal welfare community to acknowledge the issues and actively seek out that  middle ground.

There are a lot of different stakeholders to this -- and I think everyone has a role in trying to do what is best for the animals that are in our care. First and foremost, it means acknowledging that the science exists. We cannot afford to bury our heads in the sand - that's how you get to let other people address the issue for you.  And it's more than just the science that shows correlations -- but it makes biological sense that removal of growth hormone-producing gonads (especially at a very young age) would lead to long term growth and development issues.  This completely passes the sniff tests, and we should take it seriously.

Where do we go from here?

It's a complex problem to be sure, and there are a lot of people with a vested interest in coming to the table with their part of the solution. 

-- For the breeding community, I've seen a fair amount of talk about calling for the end of spay/neuter. Obviously this is self-serving to their needs. This community MUST acknowledge the sheltering realities that exist and that some form of population control is currently necessary in order to help maintain the drops in shelter euthanasia that have taken place over the last 2 decades.

-- For the lawmaking community, stop making laws mandating spay/neuter. It was never a good idea, but especially in light of the current research, there are many good experts in the field that are in disagreement with what the right solutions are. Please leave spay/neuter to the veterinary community so they may make judgment calls based on the best science available. Mandating spay/neuter does not do that. I've seen many a law that is requiring sterilization at very young ages and it seems evident that this is not in the best interests of the pets we claim to be protecting.

-- For the science community, we now have 3 studies that examine the impacts on dogs. All three have been on large-breed dogs. We need more research to also include small dogs, and cats, to determine if the risks are as severe with those as well. The more we understand about the scale and scope of the problem the better.

-- For the veterinary community, let's begin teaching other methods of sterilization. Zeuterin certainly seems to have its proponents and is one solution. But an even simpler one may be to begin performing vasectomies and tubal ligations instead of neuters & spays so that growth hormones can remain in place. However, most vets do not currently perform these proceedures. That needs to change and quickly.

-- For the shelter/rescue community, maybe we need to start waiting to alter puppies until they are older? Do we really need to alter 2 month old puppies? Would we be better off waiting until they were at least 6 months of age?  The same purpose would be served, but for every month you wait, the less of an increase in many of the health risks you have -- especially for large breed and giant puppies. It certainly seems like there is a happy medium here. 

This is a gnarly and complex issue -- and definitely a lot that is still unknown. But if all parties are willing to come together to acknowledge the risks, on all sides, I think a viable solution is out there. But it must first start with acknowledgment and open communication. 

Comments

[Stacey]

I know several breeders. NONE are calling for the end of spay/neuter. These people DO NOT want to be the cause of any more animals in a shelter. What I have seen are some breeders that will void the health warranty if the dog is spayed/neutered before a year of age. This seems like a good compromise to me.

[Michael Kitkoski]

Thanks for posting this, Brent. I think it would behoove all of us to take a wait-and-see - albeit vigilant - attitude. As we've seen recently with research into mammograms, the science can often be conflicting. This research seems to have been done primarily on purebred dogs where the occurrence of cancer and other genetic diseases can be more prevalent. In addition to smaller breeds, how are mixed-breed dogs affected by juvenile spay/neuter? We simply don't know. It's way too early to abandon juvenile spay/neuter, but we need to keep our eyes open.

[Brent]

And while keeping our eyes open, also looking for other options.

I think it is important to do purebreds first -- it certainly takes one big factor (breed) out of the equation. But thus far we've not been able to isolate other factors (like diet, environmental contaminants, etc) but given that there are major similarities across three breeds of study it is a watchout -- and again, I think passes the sniff test of what we know about gonadal hormones and development.

But yes, it is early, and probably not time to throw out viable solutions yet, but we do need to be looking for new ones...and probably quickly.

[dodo]

"regardless of age of neuter."

This is not true. Look at table 2(http://img841.imageshack.us/img841/1479/n2aj.png)

Mast cell cancer is 3.5x higher across all neutered age group but it is not the same regardless of age of neuter. The risk for those neutered after 12 months is 4.5x, the risk for those neutered 7-12 months is 2.0, the risk for before 6 months is 2.8x. This pattern where the risk is highest for dogs neutered after 12 months applies to all the cancer categories.

If were are going to attribute the differences in risk to the effect of neutering, then we have to conclude that neutering before 12 months is much safer than neutering after. And overall(see the category "all cancer combined") neutering before 6 months is actually marginally safer than neutering at 7-12 months.

So your claim that "juvenile spay/neuter (before 6 months) heightens the risk." is not backed up by this study.

(The authors did have one plausible explanation for the increased risk for the after 12 months group. When a dog gets cancer, a breeder may choose to neuter related dogs, who then go on to get cancer.)

[Triangle]

I also think that the animal loving community needs to stop labeling all owners with unspayed pets are 'irresponsible', regardless of circumstances or reasoning. My own animals have always been s/n...a choice that may change in the future (such research was no available when I last adopted a pet and so did not factor into my decision making.) But I have a family member who delayed neutering her large breed dog based on the early studies, and has been constantly berated and belittled for doing so by others in the rescue community. The dog was never bred, but that didn't matter in the least. A responsible owner makes the best decision they can for their pet based on that pet's individual circumstances...period.

[Selma]

Most breeders I know want the owners of their pet puppies to neuter - at the appropriate age.

In my breed, early neutering in males results in distortions such as long, skinny legs, small heads and a lack of those beautiful secondary male characteristics.

I agree that for most pet owners, keeping an intact bitch can be a burden, although it really doesn't need to be.

I was just saying the other day that if I were to neuter a male (unlikely, since there is no evidence supporting it), I'd go for a vasectomy so they would still get the benefits of the hormones.

There are a LOT of studies out there, the majority showing long term health risks and little benefit in males, with some health benefit in females such as avoidance of pyrometra and mammary/other reproductive cancers.

[Selma]

Well, that belief of mine has been challenged, re neutering and mammary tumours:

http://www.ncbi.nlm.nih.gov/pubmed/22647210

J Small Anim Pract. 2012 Jun;53(6):314-22. doi: 10.1111/j.1748-5827.2011.01220.x.
The effect of neutering on the risk of mammary tumours in dogs--a systematic review.
Beauvais W, Cardwell JM, Brodbelt DC.
Author information
Abstract
A commonly-stated advantage of neutering bitches is a significant reduction in the risk of mammary tumours, however the evidence for this has not previously been assessed by systematic review. The objectives of this study were to estimate the magnitude and strength of evidence for any effect of neutering, or age of neutering, on the risk of mammary tumours in bitches. A systematic review was conducted based on Cochrane guidelines. Peer-reviewed analytic journal articles in English were eligible and were assessed for risk of bias by two reviewers independently. Of 11,149 search results, 13 reports in English-language peer-reviewed journals addressed the association between neutering/age at neutering and mammary tumours. Nine were judged to have a high risk of bias. The remaining four were classified as having a moderate risk of bias. One study found an association between neutering and a reduced risk of mammary tumours. Two studies found no evidence of an association. One reported "some protective effect" of neutering on the risk of mammary tumours, but no numbers were presented. Due to the limited evidence available and the risk of bias in the published results, the evidence that neutering reduces the risk of mammary neoplasia, and the evidence that age at neutering has an effect, are judged to be weak and are not a sound basis for firm recommendations.
© 2012 British Small Animal Veterinary Association.

[MichelleD]

Part of the problem is in the past, people have been suckered by the "no studies have shown any ill effects resulting from pediatric neuter".

That was because THERE WERE NO STUDIES on pediatric neuter AT ALL!! (At the time at least..)

I have to say, I have no interest whatsoever in having an un-altered cat in my house. I can say with certainty that my female cat's life expectancy was down to minutes after a couple days of that experience. ;-)

[Brent]

Thanks Selma for the info.

Triangle -- completely agree with you that we do need to turn the conversation toward those who have chosen not to spay/neuter to be a respectful conversation.

Dodo -- you are correct -- the negative impact for the Vizsla study does not seem to be driven by pediatric spay/neuter -- however, the other three studies that I linked to did have that as a common denomenator so I felt it was worth mentioning.

[Lori S.]

This is important research, and I will be following this as more research is done. I notice that certain fears and phobias were more common in neutered Vizslas, but aggression was not measured; I would be very interested in aggression measures for neutered vs. non-neutered dogs.

One thing to note, directly from the study: "Relationships between gonadectomy, sex, and death (all causes): When controlling for sex, the odds of a gonadectomized Vizsla being deceased were not significantly (P= 0.990) different for dogs that were gonadectomized,
compared with the odds for sexually intact dogs, regardless of the age at which the dog was spayed or neutered. There was no significant (P= 0.595) difference in the longevity of gonadectomized Vizslas, compared with the longevity for those that remained sexually intact).

In other words, while these particular cancers were more likely in neutered dogs, neutered dogs had the **same life expectancy** as non-neutered dogs (who were, presumably, dying from other causes at, on average, the same age). This is very important - just because certain cancers are more prevalent with neutering, it does not appear that the neutered dogs have a shorter lifespan!

[dodo]

Selma, the thing is, if you apply the analysis used in the systemic review on any other health or behavior issues associated with neutering, you will likely come to the same conclusion, that evidence for any association between neutering and any condition is weak at best.

The review article is open access.(http://onlinelibrary.wiley.com/doi/10.1111/j.1748-5827.2011.01220.x/full) You can take a look at it(or the one on urinary incontinence by the same authors http://onlinelibrary.wiley.com/doi/10.1111/j.1748-5827.2011.01176.x/full) and see how they judge the quality of a study, then use them to judge other studies that shows positive or negative effects associated with neutering. They are all low quality.

[Lis Carey]

"-- For the breeding community, I've seen a fair amount of talk about calling for the end of spay/neuter. Obviously this is self-serving to their needs. This community MUST acknowledge the sheltering realities that exist and that some form of population control is currently necessary in order to help maintain the drops in shelter euthanasia that have taken place over the last 2 decades."

What a bizarre thing to say.

Every single responsible breeder I'm aware of has a spay/neuter clause in their pet puppy/kitten contracts. Some of the dog breeders have been reevaluating the age at which the pet puppy needs to be spayed/neutered BASED ON THE MOUNTING SCIENTIFIC EVIDENCE against early spay/neuter, but they are not changing their basic position that pet-quality puppies placed with people who want pets and not the work of learning to be responsible breeders, need to be spayed/neutered.

Many of them are actively involved in rescue themselves, or support rescue in other ways. They do not want to reverse the gains made in recent years, and they certainly do not want the risk of dogs or cats of their breeding or from their lines winding up in shelters.

So what exactly is this statement based on?

[Galway]

Wait a minute! This is hardly the first article on the negative effects of spay/neuter. If there is ANY question at all that the procedure may not be doing our dogs any good, and may in fact be doing great harm, shouldn't the very first step be to STOP DOING IT? It's already been proven many times that education is the key and that mandatory spay/neuter is a huge FAIL, but that's still beside the point. If there is even the smallest chance that removing healthy organs from my dog could be a bit risky, I'm joining the rest of the civilized world and stop doing it, until and unless I see proof that it's safe. What is there to discuss? If there is anything that has even the slightest potential for harming my dog, I'M NOT DOING IT. Are you all crazy? Or am I the only one who actually CARES about my dog's health?

[Geneva Coats]

Oh my. HEAVEN FORBID that breeders should advise buyers to avoid practices that aren't in the best interest of their dog's health and well-being. But, you are wrong when you state that breeders want to eliminate routine spay-neuter. In fact, most all breeders buy into this nation's speutermania campaign and are convinced that no one but them should be allowed to breed. The vast majority sell on spay-neuter contracts. Almost all dogs in our country are neutered, and we sit back and wonder about the explosion in health problems and shortened lifespans in our dogs. No mystery there.
In the US, we no longer have any dog overpopulation problem. Indeed, currently shelters in many areas have to IMPORT dogs from other regions and even other countries to have any available for adoption. Shelters where killing is the norm, do so out of their own leadership failure.
Where do you get the idea that “population control” = spay/neuter? There is absolutely NO proof that the overall nationwide decline in shelter numbers is due to the aggressive spay-neuter mentality in this country. This is a fallacious assumption. Instead, it would seem that, as in every other civilized nation where there is no significant dog population problem, education regarding responsible ownership and keeping your dog leashed/confined, is more than likely the real reason.
If an owner allows his dog to roam, the dog has bigger problems than an unexpected litter. Like being killed by traffic or other animals. Neutered dogs are not immune from the ill effects of roaming.
Just say NO to routine spay-neuter without genuine medical necessity. Allow the owner to make their own informed choice, but make sure that people are aware of the risks involved with choosing to spay or neuter. Currently, FEW people are informed about the health effects of spay and neuter. The assumption by most is that it's good for your dog.

[Geneva Coats]

Oh, BTW, there are DOZENS of studies about spay-neuter that arrive at the same conclusion. Not just three.
http://time4dogs.blogspot.com/2010/12/rethinking-spay-and-neuter.html

[Brent]

Gallaway/Geneva,

It should be noted that still the #1 cause of death of healthy pet animals in this country is being killed in animal shelters.

Yes, spay/neuter has proven to be 100% effective against having unplanned litters - -which has proven to decrease the population of animals.

I think denying the challenges faced in shelters in this country is both reckless and negligent.

I agree that people need to make an informed decision. That's why I posted this. However, I think it's important that we smartly weigh all sides of an issue. Do risks increase? It appears that that may be the case -- although we don't know for certain the degree of the increase and we also don't know if it's immediately causal (ie, in none of the studies have other factors such as environmental exposures and diet been excluded).

That said, there is certainly enough evidence to make exploring other ways of population control a necessity.

[Diane Chicarelli]

"I can say with certainty that my female cat's life expectancy was down to minutes after a couple days of that experience. ;-)"

Posted by: MichelleD

I literally laughed out loud at this, MichelleD. Yeah, it only takes once, doesn't it? By day two I was counting the days until her spay appointment.