Do routine, elective gonadectomies really increase dogs’ lifespan?

Methodology of studies should be carefully assessed before accepting the association between being gonadectomized and lifespan reflects a causal relationship

Neutering is perceived to impact the lifespan of dogs, but other factors may also come into play, such as breed.Photo © Getty Images
Neutering is perceived to impact the lifespan of dogs, but other factors may also come into play, such as breed.
Photo © Getty Images

A Google search shows many veterinary and animal-welfare websites claim neutering prolongs the lifespan of male and female dogs. Certainly, many studies1-10 have reported a consistent association between canines being gonadectomized and longer average lifespan—several months to two years longer in females, and none to over a year longer in males.

However, the methodology of these studies should be carefully assessed before accepting that the association between being gonadectomized and lifespan reflects a causal relationship (i.e. that neutering really does prolong lifespan).


These studies1-10 are retrospective analyses of populations consisting of many breeds with widely varying average lifespans, and utilized “dichotomous binning,”11 in which dogs were categorized as neutered or intact depending on their neuter status assessed when they died. So, they took no account of the age at which dogs were neutered—of how long the dogs had been exposed to gonadal hormones—which was likely the major determinant of any effects of gonadectomy on dogs’ physiology, health or behavior that might result in any changes in their lifespan.

Retrospective epidemiological studies to identify and quantify associations present in population data are often fraught with confounding factors. This article explains multiple artefacts that affected the association between neuter status and lifespan in these studies, such that the studies’ results do not reliably indicate how much—or even whether—neutering influences average lifespan.

Five confounding artefacts

  • Forward causation: If the biological effect of neutering causally alters—whether increasing or decreasing—average lifespan, that can be called forward causation. However, in these studies,1-10 several factors other than neutering also acted to cause an association between neuter status at death and lifespan, which was not a biological effect of neutering.

None of these factors are mutually exclusive, and their effects on the association between neuter status and lifespan are indistinguishable from, and will sum with, any effect of forward causation, confounding interpretation of lifespan differences between neutered and intact dogs as evidence of forward causation.

  • Reverse causation: The longer an intact dog lives, the more opportunity there is for it to be neutered and reasons for neutering increase with age. Given a longer life makes being neutered more likely, all else being equal, there will be an association between being neutered and longer average lifespan, but the direction of causality is the reverse of that where neutering causally
    affects lifespan.
  • Census effect: All gonadectomized animals were intact and alive until the surgery. So, dogs identified at death as intact could have died at any age, but dogs identified at death as neutered could have died only after the age at which they were neutered. All else being equal, therefore, the neutered population is, on average, older than the population of intact animals.
  • Incorrect classification of intact dogs as neutered: Some studies, instead of calculating average lifespan from age-at-death data,1-4,6 estimated average lifespan from the distribution of mortality by age, either by calculating the proportion of age-specific mortality in each year-of-age bin7,10 (or wider age bins)5,7 or from Kaplan-Meier survival curves.8,9

However, because neuter status was categorized only at death, many intact dogs were incorrectly categorized as neutered when at ages younger than the age at which they were actually neutered. This incorrect categorization reduced for intact dogs, and increased for neutered dogs, the apparent number of surviving dogs at each age, thereby artefactually increasing and decreasing the apparent mortality of intact and neutered dogs, respectively.

One study,9 after analyzing the association of neutering and lifespan across all dogs in their study population, repeated their analysis including only dogs five years or older. Doing so effectively eliminated the apparent survival advantage of neutering for males and reduced it for females.

  • Spurious correlations: As all veterinarians know, correlation does not necessarily imply causation. Spurious correlation refers to a third factor correlated to, and influencing, both neuter status and lifespan.

Neutering is perceived to be part of responsible ownership in some of the countries where studies of its effects on lifespan have been done, and so it may be a proxy for better husbandry and medical care.12 If owners of neutered dogs provide better care (i.e. diet, vaccinations, parasiticide usage, pet insurance, medical care when ill, etc.) than owners of intact dogs,13,14 and that better care increases lifespan, that would result in neutered dogs having a longer average lifespan, although that longer lifespan would not be a biological effect of neutering.

  • The dog populations studied1-10 consisted of many different dog breeds, including mixed-breed: Mixed-breeds have a longer average lifespan than the average for pure breeds.2,6,8-10,15-18 Mixed-breeds are also more often neutered than purebred dogs,13,14,19,20 resulting in more mixed-breed (longer lived) ending up in the neutered-dog population than the intact-dog population, making a spurious association between being neutered and a longer average lifespan.

Similarly, smaller breeds have substantially longer lifespans, on average, than larger breeds.2,6,8-10,15,16,18,21,22 The proportion of dogs neutered varies widely between breeds,14,23 although little information is available regarding the proportions of each breed neutered in any country.

If, on average, the proportion of each breed neutered covaried with breed size, perhaps because of owner socioeconomic, household or population demographic factors,13,14 or variation across breeds in management requirements at home or disease profiles–and small breeds may be more likely to be neutered simply because they live longer–that would result in a positive or negative association between being neutered and lifespan. Again, the association would not be a biological effect of neutering.

In the one study of a heterogeneous population that also separately analyzed individual breeds within that population,7 neutering was a significant factor affecting longevity in “more than half” of the 25 breeds assessed. Three other studies24-26 investigated one breed only and used dichotomous binning of neuter status at time of death.

In necropsied golden retrievers from a U.S. referral hospital population, being gonadectomized was associated with a longer lifespan in females, but not males.24 In the vizslas in the U.S., being gonadectomized was not associated with lifespan in data for males and females combined.25 In Swiss Bernese mountain dogs, being gonadectomized was not associated with a significant survival difference in males or females.26

The association between being gonadectomized and longer lifespan in individual breeds appears less consistent than in studies of heterogeneous breed populations.


Some of the discussed artefacts definitely, and others probably or possibly, increase the association between being neutered and longer lifespan. These artefacts each sum with any genuine effect (whether positive or negative) of neutering on lifespan.

The magnitude and direction of any genuine effect of neutering on lifespan is unknown, and the magnitudes of each of the artefacts are unknown.

Clearly, however, studies utilizing dichotomous binning of neuter status at time of death, particularly in a heterogeneous population of dogs, do not provide reliable evidence of the effect of neutering on lifespan—it is not even clear from their results whether neutering increases or decreases lifespan in either females or males.

The two studies that accounted for both age at neutering and breed heterogeneity (See “Breed-specific studies that accounted for age at neutering”) found being neutered was associated with substantially shorter
average lifespan.

To answer the question in the title of this article: The available evidence does not show that gonadectomy increases dogs’ average lifespan–in fact, gonadectomy may possibly shorten it.


Two studies27,28 investigated one breed only and accounted for age at neutering—effectively assessing the ‘dose-response’ relationship between duration of exposure to gonadal hormones and longevity.

One studied only female Rottweilers,27 the other studied boxers, but only up to 10 years old, and combined both sexes in their analysis.28 Both studies found being gonadectomized was associated with substantially lower survival. Both studies directly compared the results obtained accounting for age at neutering with the results from the same data analyzed using dichotomous binning of neuter status at time of death. In both studies, the association between neuter status and survival reversed from negative when accounting for age at neutering to positive when dichotomous binning was used.

The results of these two studies27,28 are not themselves free of artefact, and the extent to which findings in Rottweilers or boxers can be extrapolated to other breeds is unknown. Clearly, however, these two studies produced results contrary to the very consistent results reported when dichotomous binning is used in heterogeneous populations of dogs.

Martin L. Whitehead, BSc, PhD, BVSc, CertSAM, MRCVS, is a member of the Evidence-Based Veterinary Medical Association (EBVMA), with different members writing this column. While all articles are reviewed for content, the opinions and conclusions of the author(s) do not necessarily reflect the views of the EBVMA or Veterinary Practice News. For information about the association or to join, visit


  1. Bronson RT. Variation in age at death of dogs of different sexes and breed. Am J Vet Res 1982;43:2057-2059.
  2. Michell AR. Longevity of British breeds of dog and its relationship with sex, size, cardiovascular variables and disease. Vet Rec 1999;145:625-629.
  3. Moore GE, Burkman KD, Carter MN, et al. Causes of death or reasons for euthanasia in military working dogs: 927 cases (1993-1996). J Am Vet Med Assoc 2001;219:209-214.
  4. Banfield State of Pet Health 2013 Report: Available at: Accessed Jan 2,2023.
  5. Hoffman JM, Creevy KE, Promislow DE. Reproductive capability is associated with lifespan and cause of death in companion dogs. PLos ONE 2013;8:e61082.
  6. O’Neill DG, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Longevity and mortality of owned dogs in England. Vet J 2013;198:638–643.
  7. Hoffman JM, O’Neill DG, Creevy KE, Austad SN. Do female dogs age differently than male dogs? J Gerontol – Biol Sci 2018;73(2):150-156.
  8. Urfer SR, Wang M, Yang M, Lund EM, Lefebvre SL. Risk factors associated with lifespan in pet dogs evaluated in primary care veterinary hospitals. J Am Anim Hosp Assoc 2019;55(3):130-137.
  9. Urfer SR, Kaeberlein M, Promislow DEL, Creevy KE. Lifespan of companion dogs seen in three independent primary care veterinary clinics in the United States. Canine Med Genet 2020;7:7.
  10. Teng KT-Y, Brodbelt DC, Pegram C, Church DB, O’Neill DG. Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom. Sci. Rep. 2022;12:6415.
  11. Waters DJ, Kengeri SS, Maras AH, Chiang EC. Probing the perils of dichotomous binning: How categorizing female dogs as spayed or intact can misinform our assumptions about lifelong health consequences of ovariohysterectomy. Theriogenology 2011;76:1496-1500.
  12. Urfer SR & Kaeberlein M. Desexing dogs: A review of the current literature. Animals 2019;9:1086.
  13. Sánchez-Vizcaíno F, Noble P-JM, Jones PH, Menacere T, Buchan I et al. Demographics of dogs, cats, and rabbits attending veterinary practices in Great Britain as recorded in their electronic health records. BMC Vet Res 2017;13:218.
  14. Trevejo R, Yang M, Lund EM. Epidemiology of surgical castration of dogs and cats in the United States. J Am Vet Med Assoc 2011;238(7):898-904.
  15. Proschowsky HF, Rugbjerg H, Ersbøll AK. Mortality of purebred and mixed-breed dogs in Denmark. Prev Vet Med 2003;58:63-74.
  16. Kraus C, Snyder-Mackler N, Promislow DL. How size and genetic diversity shape lifespan across breeds of purebred dogs. GeroScience 2022. doi: 10.1007/s11357-022-00653-w. Online ahead of print.
  17. Inoue M, Kwan NCL, Sugiura K. Estimating the life expectancy of companion dogs in Japan using pet cemetery data. J Vet Med Sci 2018;80(7):1153-1158.
  18. Yordy J, Kraus C, Hayward JJ, White ME, Shannon LM et al. Body size, inbreeding, and lifespan in domestic dogs. Conserv Genet 2020;21(1):137-148.
  19. Turcsán B, Miklósi Á, Kubinyi E. Owner perceived differences between mixed-breed and purebred dogs. PLoS ONE 2017;12(2):e0172720.
  20. da Costa REP, Kinsman RH, Owczarczak-Gerstecka SC, Casey RA, Tasker S, et al. Age of sexual maturity and factors associated with neutering dogs in the UK and Republic of Ireland. Vet Rec 2021;191(6):e1265.
  21. Galis F, van der Sluijs I, van Dooren TJM, Metz JAJ, Nussbaumer M. Do large dogs die young? J Exp Zool (Mol Dev Evol) 2007;308B:119-126.
  22. Adams VJ, Evans KM, Sampson J, Wood JLN. Methods and mortality results of a health survey of purebred dogs in the UK. JSAP 2010;51:512-524.
  23. Royal Veterinary College, VetCompass Breed health publications: Accessed 2 Jan 2023.
  24. Kent MS, Burton JH, Dank G, Bannasch DL, Rebhun BR. Association of cancer-related mortality, age and gonadectomy in golden retriever dogs at a veterinary academic center (1989-2016). PLoS ONE 2018;13(2):e0192578.
  25. Zink MC, Farhoody P, Elser SE, Ruffini LD, Gibbons TA, Rieger RH. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. J Am Vet Med Assoc 2014;244(3):309-319.
  26. Klopfenstein M, Howard J, Rossetti M, Geissbùhler U. Life expectancy and cause of death in Bernese mountain dogs in Switzerland. BMC Vet Res 2016;12:153.
  27. van Hagen MAE, Ducro BJ, van den Broek J, Knol BW. Life expectancy in a birth cohort of Boxers followed up from weaning to 10 years of age. Am J Vet Res 2005;66(9):1646-1650.
  28. Waters DJ, Kengeri SS, Clever B, Booth JA, Maras AH et al. Exploring mechanisms of sex differences in longevity: Lifetime ovary exposure and exceptional longevity in dogs. Aging Cell 2009;8:752-755.

Post a Comment

3 thoughts on “Do routine, elective gonadectomies really increase dogs’ lifespan?

  1. Dr. Whitehead,

    Thank you for your excellent article “Do Routine, Elective Gonadectomies Really Increase Dogs’ Lifespan?” As someone who has long believed the answer to this question to be “Yes,” I appreciate the opportunity to critically review my belief and its evidentiary foundations.

    The methodological weaknesses you identify in studies of this question are significant and certainly should impact our confidence in the conclusions based on these data. Consistency in the direction of findings can be an argument for a true effect but, as you point out, it could also be a function of the consistent direction of sources of bias.1

    In the face of such uncertainty, it might be worthwhile to consider the larger context of studies evaluating the impact of neutering on life expectancy in other species, as well as possible sex differences in these effects.

    Perhaps the ideal study to evaluate the effect of neutering on lifespan would be a prospective trial of comparable animals randomly assigned to neutering or sham procedure at the same age and followed for a lifetime. While this is unlikely to happen with dogs, such studies have been done in rats and mice.2-8

    These typically show an increase in lifespan for males and a decrease for females associated with neutering (though there are some studies which do show benefits to females as well). Interestingly, administration of estrogen often appears to increase lifespan in both males and females, while administration of testosterone decreases longevity in both sexes. Testosterone seems very much the “bad guy,” at least with regard to rodent longevity.

    Of course, dogs aren’t rodents. The limited evidence we have more often shows the greatest longevity benefit in neutered female dogs rather than in males. This may be an artifact of the limitations you point out, but it could also reflect the significance of sex-specific causes of mortality impacted by neutering, such as mammary neoplasia and pyometra.9-10 (but see also11)

    There is less rigorously controlled evidence from other species that also suggests neutering increases lifespan in males and decreases it in females, including sheep12-13, rhesus macaques14, and possibly humans15-17 (though not surprisingly, there is significant contention over the human evidence18-19).

    There is also a rich and equally contentious literature concerning the potential tradeoff between reproduction and lifespan in many species.20-22 There is evidence that suppression of reproduction by various means may divert resources to somatic maintenance in a way that extends lifespan. There are even some intriguing, but by no means thoroughly demonstrated, potential mechanistic explanations for this apparent connection.23 Of course, this evidence too has its limitations and contradictions, but it provides a potential plausible rationale for why neutering might extend lifespan in dogs, and biologic plausibility is one important criterion in making judgements about causal relationships.1

    As a general practice clinician and proponent of evidence-based medicine, and now a researcher in geroscience, I have spent many hours wading through the complex and conflicting evidence concerning if and when neutering might have a net health benefit for my canine patients. I do not expect an unassailable and universal recommendation to emerge any time soon, or ever. The uncertainty leaves room for a variety of approaches, each of which should be rationally derived from the available evidence and proposed with a degree of confidence proportional to the limitations of that evidence. Thank you again for your contribution to this fascinating and important subject.

    Brennen McKenzie, MA, MSc, VMD

    1. Hill AB. The environment and disease: Association or causation? Proc Royal Soc Med. 1965:58 (5);295–300.
    2. Garratt M. Try H. Brooks RC. Access to females and early life castration individually extend maximal but not median lifespan in male mice. Gerosci. 2021;43(3):1437-1446.
    3. Asdell SA. Doornenbal H. Joshi SR et al. The effects of sex steroid hormones upon longevity in rats. Reprod. 1967;14(1):113-120.
    4. Drori D. Folman Y. Environmental effects on longevity in the male rat: exercise, mating, castration and restricted feeding. Exp Gerontol. 1976;11(1-2):25-32
    5. Benedusi V. Martini E. Kallikourdis M. et al. Ovariectomy shortens the life span of female mice. Oncotarget. 2015;6(13):10801-11.
    6. Asdell SA. Joshi SR. Reproduction and longevity in the hamster and rat. Biol Reprod. 1976;14(4):478-80.
    7. Iwasa T, Matsuzaki T, Yano K, et al. The effects of ovariectomy and lifelong high-fat diet consumption on body weight, appetite, and lifespan in female rats. Horm Behav. 2018;97:25-30.
    8. Arriola Apelo SI. Lin A. Brinkman JA. et al. Ovariectomy uncouples lifespan from metabolic health and reveals a sex-hormone-dependent role of hepatic mTORC2 in aging. Elife. 2020;9:e56177
    9. Beaudu-Lange C. Larrat S. Lange E. et al. Prevalence of Reproductive Disorders including Mammary Tumors and Associated Mortality in Female Dogs. Vet Sci. 2021;8(9):184.
    10. Sundburg CR. Belanger JM. Bannasch DL. Et al. Gonadectomy effects on the risk of immune disorders in the dog: a retrospective study. BMC Vet Res. 2016;12(1):278.
    11. Beauvais W. Cardwell JM. Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs–a systematic review. J Small Anim Pract. 2012;53(6):314-22..
    12. Jewell P. Survival and behaviour of castrated Soay sheep (Ovis aries) in a feral island population on Hirta, St. Kilda, Scotland. J Zool. 1997;243:623-636.
    13. Sugrue VJ. Zoller JA. Narayan P. et al. Castration delays epigenetic aging and feminizes DNA methylation at androgen-regulated loci. Elife. 2021;10:e64932.
    14. Kessler MJ. Wang Q, Cerroni AM, Grynpas MD, Gonzalez Velez OD, Rawlins RG, Ethun KF, Wimsatt JH. Kensler TB. et al. Long-term effects of castration on the skeleton of male rhesus monkeys (Macaca mulatta). Am J Primatol. 2016;78(1):152-66.
    15. Min K. Lee C. Park H. The lifespan of Korean eunuchs. Curr Biol. 2012;22:R792–R793.
    16. Parker WH. Feskanich D. Broder MS. Et al. Long-term mortality associated with oophorectomy compared with ovarian conservation in the nurses’ health study. Obstet Gynecol. 2013;121(4):709-716.
    17. Hamilton JB. Mestler GE. Mortality and survival: comparison in white subjects of data for 297 eunuchs, 735 intact males, and 883 intact females. Anat Rec. 1969a;163:194.
    18. Nieschlag E. Nieschlag S. Behre HM. Lifespan and testosterone. Nature. 1993;366(6452):215.
    19. Le Bourg É. No Ground for Advocating that Korean Eunuchs Lived Longer than Intact Men. Gerontol. 2015;62(1):69-70.
    20. Aguilaniu H. The mysterious relationship between reproduction and longevity. Worm. 2015 Mar 6;4(2):e1020276.
    21. Brooks RC. Garratt MG. Life history evolution, reproduction, and the origins of sex-dependent aging and longevity. Ann N Y Acad Sci. 2017;1389(1):92-107.
    22. Bolund E. Lummaa V. Smith K. et al. Reduced costs of reproduction in females mediate a shift from a male-biased to a female-biased lifespan in humans. Sci Rep. 2016’6, 24672
    23. Hansen M. Flatt T. Aguilaniu H. Reproduction, fat metabolism, and life span: what is the connection? Cell Metab. 2013;17(1):10-9.

  2. Dear Martin,

    It’s always a pleasure to read your thoroughly argued pieces and there is no doubt that this complex issue has been rather brushed over by many in our profession on the understanding that because a long series of papers seems to indicate that neutering of female dogs at least benefits lifespan there is no reason to examine the issue more thoroughly.

    However, I do take issue with your article over one very crucial point. For intact bitches there is a very high incidence of the development of endometritis / pyometra and the incidence of that condition increases with age. When I first qualified (1981) by far the most common surgical emergency we saw in companion animal practice was a “pyo.” Whilst non-surgical treatment of this condition is possible surgical treatment remains the preferred option and has an excellent survival rate (Gibson A, Dean R, Yates D, Stavisky J. (2013) A retrospective study of pyometra at five RSPCA hospitals in the UK: 1728 cases from 2006 to 2011. Vet Rec. 2013;173(16):396.) In the last 40 years or so desexing of female dogs in the UK when they are young has become the norm, so pyometra is no longer such a common condition, consequently the crucial importance of this problem has receded in our minds. All dogs treated surgical for pyometra obviously become neutered . Most of these would have died if they were left intact.

    In the Scandinavian countries, where neutering of bitches for management reasons is considered to be unethical, or even illegal, it has been shown that many, many dogs develop endometritis/pyometra. (Jitpean, S.; Hagman, R.; Strom Holst, B.; Hoglund, O.V.; Pettersson, A.; Egenvall, A. Breed variations in the incidence of pyometra and mammary tumours in Swedish dogs. Reprod. Domest. Anim. 2012, 47, 347–350.

    I believe that once account is taken of the latent risk of pyometra in intact bitches then the apparent benefit of neutering upon lifespan becomes untangled. All surgical procedures incur some risk and the surgical neutering of a healthy young bitch is no exception but the surgical risks are definitely higher in an older bitch suffering from endomteritis./ pyometra. Moreover, these sick animals are systemically unwell. From the welfare perspective alone surely the reduced incidence of this condition has been a bonus to dogs lives?

    Thaks again for your interesting article

    Chris Little BVMS PhD DVC FRCVS,
    RCVS Recognised Specialist in Veterinary Cardiology.