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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Spayed and Neutered Dogs Live Longer

We talked recently about a study that revealed an increase in the incidence of some significant diseases in neutered male and female dogs in comparison to intact individuals. Disease incidence is important, but the statistic that is of greatest interest to most pet owners is survivability, in other words, “what effect will a particular decision (e.g., neutering) have on my dog’s lifespan.”


Research published on April 17, 2013 in the online journal PLoS ONE looked at the decision to neuter dogs with that endpoint in mind. Based on the debate that surrounded my previous post, the results of this study might surprise some of you.


Looking at a sample of 40,139 death records from the Veterinary Medical Database from 1984-2004, scientists from the University of Georgia determined the average age at death for dogs that had not been spayed or neutered was 7.9 years versus 9.4 years for sterilized dogs. Dogs that had been spayed or neutered were more likely to die from cancer or autoimmune diseases while those that were not 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 sterilized," said Jessica Hoffman, a UGA doctoral candidate who co-authored the study.


Researcher Kate Creevy added, "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."


The authors offer potential explanations for these observations in the PLoS ONE paper:


Sterilization increased the risk of death due to neoplasia, but did not increase risk for all specific kinds of cancer. Female dogs sterilized before sexual maturity are unlikely to develop mammary cancer because of the decrease in cumulative estrogen exposure associated with the absence of the estrus cycle[30]. However, it is not clear why the frequency of some cancers outside the reproductive system, including lymphoma and osteosarcoma, is influenced by sterilization, while the frequency of others, such as melanoma and squamous cell carcinoma, is not. The increased risk of death due to cancer observed in sterilized dogs could be due to the fact that in both sexes, dogs sterilized before the onset of puberty grow taller than their intact counterparts[31] as a result of reduced estrogen signaling [32]. Recent studies in humans suggest that growth is a risk factor for a number of different cancers[33].


Conversely, sterilized dogs had a decreased risk of death due to infection, and avoidance of infection may partly explain their longer lifespans. The relationship between sterilization and infectious disease could arise due to increased levels of progesterone and testosterone[34] in intact dogs, both of which can be immunosuppressive[35], [36]. Studies in humans, mice and rats reveal patterns of infectious disease morbidity and mortality associated with testosterone and estrogen exposure. However, these patterns vary with host species, type of pathogen, and chronicity of infection[37]. Additionally, sterilization and disease risk might both be correlated with specific canine behaviors. Given the opportunity, intact male dogs are more likely than sterilized dogs to roam, and to fight with other dogs, and intact female dogs show more dominance aggression than spayed females[38],[39]. These behaviors might increase the risks of both infectious and traumatic causes of death among intact dogs.


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. Animals included in the study had been referred to a veterinary teaching hospital and represent a population of sick animals.


"The overall average life span is likely shorter than what we would observe in private practice, because these were dogs seen at teaching hospitals, but the difference in life span between sterilized and intact is real," Creevy said. "The proportionate effects on causes of death are translatable to the global dog population, and it will be interesting to see if explanations for these effects can be found in future studies."


Dr. Jennifer Coates



Hoffman JM, Creevy KE, Promislow DEL (2013) Reproductive Capability Is Associated with Lifespan and Cause of Death in Companion Dogs. PLoS ONE 8(4): e61082. doi:10.1371/journal.pone.0061082

Comments  22

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  • ovaries and longevity
    06/20/2013 03:45pm

    http://www.dogster.com/lifestyle/preliminary-research-suggests-unspayed-dogs-may-live-longer What do you think?

  • 06/22/2013 09:33pm

    I think this link's author is clearly displeased with the findings of the Rottweiler study, but she is refreshingly honest, something that I find quite rare in discussions of the decision to spay or neuter your pet. She knows a good, worthwhile study when she sees one, and the Waters study is the best so far. I had the pleasure or attending a celebration visit of The Old Grey Muzzle Tour last March, at my vet's clinic, with an inspiring talk by Dr. Waters. I am not a scientist, but Dr. Waters' spoke so passionately in layman's language, it all made perfect sense. His talk was filled with common sense and useful information that I, as a lifetime dog owner can understand and put into practice. The politics of the animal rights movement is deeply embedded within this discussion, embedded so deeply that most dog lovers can't understand what it means if all the dogs are spayed or neutered. (Do we understand that "animal rights means no animals left" yet?) The "dogster" writer was quite insulting towards average dog owners She suggested that almost everyone is just too stupid and careless to prevent unwanted litters, so it must be up to people like her to alter all pets immediately, and give us what turns out to be misleading information on the reasons. I have had dogs in my life for more than 60 years, and only a couple of them have been S/N, and the one and only bitch that I had spayed at 6 months - because everyone said I must - developed ALL of the disorders that correlate to early S/N - hypothyroid at age 4, cruciate ligament tear at age 8, ending a successful nationally ranked agility career, and she died of hemangio sarcoma at age 10. I will never do that to a female dog again, I promise! As for the dozens of intact dogs I have owned, well, including my entire extended family of intact-dog owners, we have never once had a litter of puppies. The writer of this article doesn't seem to believe that average people can be trusted to own dogs, because if they are too stupid to understand dog reproduction cycles, they really should have pet rocks. But, it is so simple - doggy birth control is this:





    . . . and common sense.

    Let's please leave altering to informed dog owners, it is invasive surgery for females, and when you look at the study posted in this blog and compare it to the Waters study, it is clear that the Waters study is far more valuable - and not political.

  • 07/06/2013 12:52am

    My experiences have been similar, though you have about ten years on me :-)

    My family has kept (intact) dogs for three generations that I know of. One of my great uncles raised wire haired fox terriers, but no one in my immediate family has bred litters, planned or otherwise.

    The few s/n I have had have been much more expensive to keep than their intact peers, and it's hard for me to believe that a dog who must endure multiple veterinary procedures is happier than one who has no need for them.

    I share your take that preventing litters is a long way from being rocket science; if two elderly and health impaired owners can prevent litters when they have three bitches and two dogs, it really can't be a major challenge. For the average pet owner, who isn't interested in maintaining a pack, the simplest solution is an intact male dog. When I was a child, the conventional wisdom on pet dog ownership was a big, black, intact dog. I see no reason why said dog should be any particular colour, but I support the theory. Anyone who can't be bothered managing a bitches cycle should skip the bitches. For most people they make less satisfactory pets anyway. I personally prefer to work bitches, but I wouldn't actively recommend them as pets, particularly to beginners.

    It might not be so hard on the pets if the owners were fully informed re s/n. I was forced this year to neuter my dog, at age seven. He has reverted to puppy coat, but I cut his ration by half immediately, and he hasn't blown up the way every other s/n I have had. The vet who wanted to spay him as a puppy told me that preventing that obesity was simple - but I'm not sure the dog is as happy as he might be. He thinks he is starving *all* the time. If that's the worst result of this, I will be grateful, and he certainly is mature, but all the same, I resented it. The issue had nothing to do with complaints or problems, it was simply a matter of the county statute which limits one to two intact or four s/n.

    As there is no mention of gender in the statute, one can only conclude the limit was designed to prevent anyone legally breeding a litter. In any case, it's hard to see how anyone with, say, two intact dogs is at risk for producing unwanted litters, or even two bitches. This is AR law at its finest; not only does it effectively outlaw breeding without explicitely saying so, but the statute naturally includes menacing clauses, provisions for daily fines up to $1k/dog/day for violations. These kinds of provisions aren't designed to protect animals from anything other than being owned. Well over 80% of the canine population is sterile anyway, due to AR dogma, and as you say, once they are all sterilized ... there go our dogs.

    It's not only dogs. We are hearing the same song with regard to breeding *any* pets or livestock, and rabbits and horses are both taking their lumps, since Sarah Conant migrated from HSUS' legal pool to run the APHIS enforcement division.

    They are as serious as a heart attack, the AR crowd. With a war chest over $100M, and their reps insinuated in positions of power in government and the universities, they have more than enough power and resources to succeed. They have a huge (illegal) lobby, and zero ethics or morals at all. Unless we want to give up our pets and sporting animals and our diet, we need to fight, actively and aggressively.

    We are not the abusers, they are.

    To the ARAs who are driving our animal laws and regulations, animal ownership IS animal abuse, by definition. We must never, never forget that.

  • 07/06/2013 03:15am

    two brilliant comments from Chenin and Hawthorne.. I cannot top those

  • 07/06/2013 04:01am

    Hey, you may not be able to top it, but you can sure add to it. I always enjoy your comments! They are always clear and to the point. What's not to like?

  • 07/08/2013 04:41pm

    Your comments are always golden, "alice", I hope you add your considerable insights, this is a topic that is far more important than most people realize. There IS a very clear risk of extinction of pet dogs coming from the animal rights movement.They have been extraordinarily successful in convincing people that all pets should be sterilized without seeing the obvious question - where will future pets come from? Most people do not realize the consequences of supporting these groups, these wolves in sheep's clothing. I truly wonder if all the fans of those chef 'reality' shows have any idea that the donation they might make to HSUS to "protect" their beloved pets (from WHAT?) will be used to make their BBQ tailgate parties extinct.

  • 07/10/2013 03:59pm

    I enjoyed your comments and hope to find a vet in the Los Angeles area who is willing to perform an ovary-sparing spay on my puppy after she has had one or two heat periods. My vet of 30 yrs. will not do this.

  • 06/20/2013 03:50pm

    If we are to factor in the ratio of intact v sterilized animals who are impounded and ultimately killed within shelters, the average lifespan of the intact group is WAY lower. I have read that the majority of such animals do not pass their second birthday.

    Granted, the early death toll of intact animals within the shelter system is not due to a medical cause, but the societal consequence of being unsterilized makes it the most deadly of all.

  • 07/02/2013 01:38pm

    societal consequences means animals that are natural are killed at shelters more then those who are "fixed'? I do not follow that . can you quote where you read this? I agree wiht chenin.. and also what "infections" are noted in the study?

  • 07/06/2013 04:17am

    Well, yes. But what are we to do? If we continue to sterilize all our pets, as the ARAs insist we do, we will end without pets.

    Yes, if the shelters get hold of an intact dog, they will find some excuse to kill it if they can. Most public shelters use kill manuals written by HSUS ... coincidence ..?

    If we want to keep our animals, we MUST fight for them. Animal owners are the only ones who can protect animals. Laws can't protect animals; laws can only punish violators. AR pet laws are primarily *ownership limitation* laws - if you can explain to me how depriving pets of homes can protect them, I am all ears. I have never been able to figure it out. The only way these laws can be construed as 'animal protection' laws is to agree with the ARAs that animal ownership = animal abuse.

    I won't s/n my dogs arbitrarily. I have had a lot of dogs and cats over the years, and my observation is that cats are more tolerant of s/n, *if* you hold them to sexual maturity before you commit them. You will probably be told that s/n of a mature animal is riskier, which it is, but not much. I have known both dog and cat owners who have lost pets to the surgery, but it's not common.

    I s/n my cats sometime after they mature, but only threat of losing them altogether will induce me to s/n any more dogs. Sometimes it really is medically necessary; I have no problem with that. I do have a problem with the one-sided s/n hype, and worse, juvenile s/n. I'm pretty sure if people actually knew the risks, they'd opt out, mostly. As I said above, if my husband and I can manage three bitches and two dogs, all living in the same house, it really can't be all that difficult. Our dogs aren't tiny toys, either - all are over fifty pounds. In that situation, all under one roof (kennels make the whole thing a piece of cake) does result in a semi-annual circus, but it's only twice a year, and only for a couple of weeks.

    A person who is unwilling to manage a bitch's cycles shouldn't own a bitch. Why is that so terrible? It's a free choice - either you are willing or not. It really isn't rocket science.

  • Apples to oranges
    06/20/2013 04:06pm

    The first time I heard of this study, my first thought was "I'll bet they didn't control for responsible vs irresponsible owners" and that appears to be the case. If you let your dog roam or fight, then of course he's not going to live as long. And in that case, it is true that an intact animal will be more likely to take advantage of opportunities to roam and/or fight. This study compares responsible, knowledgeable owners who leave their pets intact specifically for health reasons - and who are able to prevent roaming, fighting and pregnancies - to owners who didn't sterilize their pets because they couldn't afford it, or just don't care enough and either way, they lack the knowledge to cope with an intact pet.

    To me, a more meaningful study would be one that compared longevity of intact vs sterilized animals who all belong to owners with similar behaviors. I would be willing to bet that if you just look at owners who train and socialize their dogs, provide appropriate medical care and keep them confined appropriately, then the intact ones will live longer than the sterilized ones.

    Otherwise, this is like comparing owners who feed a well-researched homemade diet to ones who feed a cat nothing but canned tuna - then saying that homemade diets are bad. Or comparing owners who thoughtfully do minimal vaccinations, while doing everything they can to support their pet's immune system with owners who don't vaccinate because they don't want to be bothered.

  • 06/20/2013 08:01pm

    Completely agree! I have two intact males. They are well trained. They listen to my voice. They are off-leash only within fenced areas. They are inside my house when I am not at home. They are not left unattended in my fenced yard even when I am at home. It's just common sense ... which is in such short supply these days.

  • 07/02/2013 01:41pm

    my neighbors neutered dog roams all of the time.. as was once sad "cutting of a dogs balls does not make him stay out of the neighbors garbage"

  • 07/06/2013 04:28am

    I suspect you are right. There are several studies, at least one European one, which found intact animals to have slightly longer life spans.

    I really don't think we can write those off to appease the ARAs. As I said above, I believe cats tolerate sterility better than dogs; we lost our old girl to a stroke at sixteen - and for the early part of her life she was an indoor-outdoor cat, which supposedly limits their lives.

    I don't see that with dogs. What I've seen with s/n dogs, a couple of my own, and many belonging to friends, is that they spend a lot more time at the vet's than I do. My s/n's have not, on the whole, lived out their lives naturally. My intact dogs have done well until they were thirteen or fourteen, I've never seen any cancers on my intact dogs, or even fatty benign tumours. Eventually something fails, and you lose them. S/n, in my experience, tend to develop one or more chronic conditions in maturity, and sometimes they can be coaxed along, but mostly they seem to die of something preventable.

    I've never seen a mammary cancer, a testicular cancer, or had a pyo among my intact dogs. Fair enough, I haven't had hundreds, but over a lifetime, you might expect to see these things we are told s/n prevents.

    Colour me skeptical ...

  • 12/04/2014 08:44pm

    Hi BBristol, My name is Jared Cantor and I am responding to a comment you posted a few years back about the article called: A Case of Chronic Active Hepatitis. The site wouldn't allow me to respond to that posting so I am reaching out to you through this one.

    I also have a Great Dane who is showing possible signs of CAH. We are going through the paces of trying to diagnose what it is exactly what my boy is dealing with. I was wondering if I would be able to connect with you and ask a few questions about your past experience with this disease? My direct email address is: [email protected]

    Any information you can provide would be greatly appreciated.

    Thank you and I am looking forward to hearing back.

    Jared and Baltimore

  • Comments
    06/20/2013 09:57pm

    The previous comments are well-reasoned and make sense. (It's so nice to read comments that aren't snarky when they disagree with the initial post!)

    However, the second paragraph of oh holland's comment makes the most sense of all.

  • 06/22/2013 09:46pm

    I agree, OldBroad. When studies use "average lifespan" based on raw numbers, statistics, the results will not be especially meaningful for individuals when it is time to consider the decision to S/N. Most of the studies of this type are biased from the beginning. It's possible to "prove" just about any pre-conceived idea with statistics.

    The Waters study stands out because it was set up to actually find more questions than answers. Dr. Waters' genius is in the idea to study well dogs, vigorous elderly dogs of a breed known for a short lifespan, in their own homes, rather than sick dogs, or disparate populations, or dogs in a hospital or shelter setting.

  • 06/25/2013 07:30am

    Well it’s true that many dog owners have their pets spayed or neutered just to help control the pet population. Adding this procedure could add up length of their lives and alter the risk of specific causes of death.

  • 07/02/2013 01:44pm

    let's be honest here.. few people castrate their dogs of othere sex to "help with "overpopulation" they do it owner convenience.. or what they perceive as that convenience

  • 07/06/2013 04:30am

    Yes, I agree. For their convenience - and because they've been told so often that it is the 'responsible' thing to do.

    Arbitrary s/n serves nothing except the AR agenda.

  • 07/08/2013 05:21pm

    I am not a scientist, I am an artist - so bear with me while I struggle with what studies like this actually mean to people like me, and the average pet owner. Yes, when you take raw statistics with such a broad base - the entire canine population in America - the numbers clearly indicate something about survival (as opposed to longevity, an entirely different term), but these raw numbers are simply not meaningful to animal owners who are looking for guidance from their veterinarian on the reproductive status of their pet.

    My frustration with the publication of these statistics is that they are always accompanied by headlines that draw a very broad conclusion. This is disingenuous. The status of stray dogs, feral animals, homeless for any number of reasons, do not relate, do not make a good basis for making the decision on whether to alter the cute puppy or adorable shelter dog that the family will be taking home for the next 10-15 years. It's apples and oranges. Of course, the typical intact shelter animal will have come from a risky situation, why would we use statistics like those in this study to guide us in our choice to alter or not? Who in the world is going to pick out a family pet and even THINK about this?

    Far more meaningful is the Rottweiler study, Dr. Waters' on-going study on LONGEVITY in family pets. THAT makes a real difference, something that we should all be paying careful attention to. My vet hosted a visit with Dr. Waters last March, part of the Old Grey Muzzle Tour, as he made his pilgrimage of sorts around the country visiting with the Rottweilers that had reached the age of 13. His presentation was inspirational. This study has practical uses for all pet owners, meaningful information. The focus is on health, wellness, looking at robust aged dogs, not on sick dogs, dead dogs, homeless dogs - admittedly a very narrow base of study. But pure genius, in my opinion.

    The outstanding facts I learned from Waters' study of vigorous, healthy Rottweilers older than 13: All the Rotties in the study were spayed or neutered by the time they were involved in the study; most of the dogs in the study are female; the primary cause of death for Rottweilers in general is osteo sarcoma at a young age; none of the studied dogs died of cancer, yet all of the dogs were harboring one or more cancers at autopsy; none of the studied dogs were altered as puppies, most of them were S/N after age 5.

    There were no other lifestyle factors that seemed to influence extreme longevity - diets were everything from Old Roy to raw, vaccinations ranged from full annual boosters to titers and 'rabies only', some were pampered pets, some were working or sports competitors, lived in climates from Alaska to Florida with environmental situations all over the place.

    The two constants with these aged dogs were these: laid back (not lazy) temperaments, and exposure to ovaries. The males didn't have quite the same strong relationships to hormone exposure, but there were positive effects from retaining testicles beyond puppy-hood. It is a significant fact that these males reached an age well beyond the average. Temperament probably plays a big role in the males, possibly reduced exposure to stress hormones.

    So it's all about the hormones. What are we doing here, insisting on altering all pets?

  • My dog's are individuals.
    01/19/2016 01:20pm

    Not the damned pet population. The facts are all female mammals get bonus "years" that they lose if they lose their ovaries before middle age including both dogs and people when women lose their ovaries before middle age they have the same average life span as a man. Another all mammal statistic is the significant increase in likelihood of prostate cancer when the testes lost. Removing a source of any hormones before the completion of puberty causes the growth plates to close at the wrong time altering the bodies of the animal and increasing their odds of hip dysplasia and other joint problems. "Fixing" an animals wreaks havoc on their systems what in hell makes people think they can play with nature without consequence. The fact that so many people think sterilization is only positive is staggering. In my opinion anybody that thinks they can change the way an organic system has functioned for all of its existence without any negative side effects is a complete and utter moron. Not to mention that certain breeds of dog like Rots are so prone to osteotoma that getting them "fixed" damn near guaranties they are going to get it if they live long enough. Not only that but in Europe sterilization is very uncommon and they do not have the pet population we do likely because they do not let money get in the way of solving a damn problem as such they outlawed puppy mills and any industrial level of breeding of pets. Oh and they rarely have accidental breeding’s for the same reason my dogs haven't gotten pregnant. They believe in something this country forgot it’s called personal responsibility. I am SMARTER than a DOG. The spca and humane society and others of their ilk mean well but they do not care about your dog or how bad altering it wantonly can affect them. They care about the population as a whole. But it is my job to care about my dogs as individuals and do what is best for THEM.

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