Scientific Results: Reproductive capability is associated with lifespan and cause of death in companion dogs
March 1, 2024 - 8 minutes readWho worked on this research?
Jessica M Hoffman
Kate E Creevy
Daniel E L Promislow
Where was it published?
PLoS One
What is this paper about?
Scientists disagree about the effect of fertility on human lifespan. Does it increase lifespan, decrease it, or have no impact on how long we live? Studies in other species, such as fruit flies and mice, suggest that reproduction sometimes, but not always, shortens lifespan. We questioned if the inconsistency of the results of earlier studies is due to the fact that they looked at when individuals died but not why they died.
In North America, companion dogs are commonly spayed or neutered at a young age for various reasons. By choosing to sterilize their dogs, dog owners have inadvertently carried out a large-scale epidemiological study on the consequences of effectively eliminating the ability to reproduce.
We looked at the causes of death for over 40,000 domestic dogs that died in veterinary teaching hospitals from 1984 to 2004. We compared causes of death in dogs that had undergone elective surgical sterilization with those that had not and measured the “lifespan cost” of keeping the ability to reproduce. We also determined the categories of disease associated with this cost.
We found that sterilization affected life expectancy by 13.8% in male dogs and 26.3% in female dogs. It also decreased the chance of death from infections. On the other hand, sterilization increased the risk of cancer, but not all specific cancers.
What do these results mean for me and my dog?
These results suggest looking closer at specific causes of death, rather than length of life alone, will greatly improve our understanding of the cumulative impact of reproductive capability on lifespan. Our results strongly demonstrate the need to determine the physiologic consequences of sterilization that influence causes of death and lifespan. Shifting the focus from when death occurs to why death occurs could also help to explain contradictory findings from human studies.
Information from our Dog Aging Project participants can also help us expand our understanding of how fertility affects dogs’ lifespans. The Dog Aging Project asks survey questions about reproductive status, giving us a chance to study the effects of fertility on the lifespan of dogs who may not have necessarily died in a veterinarian teaching hospital.
This paper was published in 2013. What new insights have been gained since then?
There have been several other complementary studies of different canine populations looking at the effects of sterilization on lifespan, as well as a comprehensive review of other DAP members. Overall, sterilization is associated with increased lifespan; however, there is still debate on the timing of sterilization on late-life health and longevity. Future studies in the Dog Aging Project will help us answer some of these questions, as we are longitudinally following puppies through adulthood, and we will have detailed information on the timing of sterilization as well as health outcomes.
Some of those papers include:
Urfer SR, Kaeberlein M. Desexing Dogs: A Review of the Current Literature. Animals. 2019; 9(12):1086. https://doi.org/10.3390/ani9121086
Urfer, S.R., Kaeberlein, M., Promislow, D.E.L. et al. Lifespan of companion dogs seen in three independent primary care veterinary clinics in the United States. Canine Genet Epidemiol 7, 7 (2020). https://doi.org/10.1186/s40575-020-00086-8
Mariana Roccaro, Romolo Salini, Marco Pietra, Micaela Sgorbini, Eleonora Gori, Maurizio Dondi, Paolo E. Crisi, Annamaria Conte, Paolo Dalla Villa, Michele Podaliri, Paolo Ciaramella, Cristina Di Palma, Annamaria Passantino, Francesco Porciello, Paola Gianella, Carlo Guglielmini, Giovanni L. Alborali, Sara Rota Nodari, Sonia Sabatelli, Angelo Peli, Factors related to longevity and mortality of dogs in Italy, Preventive Veterinary Medicine, Volume 225,2024,106155, ISSN 0167-5877,https://doi.org/10.1016/j.prevetmed.2024.106155.
Where can I learn more?
Hoffman JM, Creevy KE, Promislow DE. Reproductive capability is associated with lifespan and cause of death in companion dogs. PLoS One. 2013 Apr 17;8(4):e61082. doi: 10.1371/journal.pone.0061082. PMID: 23613790; PMCID: PMC3629191.
Abstract
Reproduction is a risky affair; a lifespan cost of maintaining reproductive capability, and of reproduction itself, has been demonstrated in a wide range of animal species. However, little is understood about the mechanisms underlying this relationship. Most cost-of-reproduction studies simply ask how reproduction influences age at death, but are blind to the subjects’ actual causes of death. Lifespan is a composite variable of myriad causes of death and it has not been clear whether the consequences of reproduction or of reproductive capability influence all causes of death equally. To address this gap in understanding, we compared causes of death among over 40,000 sterilized and reproductively intact domestic dogs, Canis lupus familiaris. We found that sterilization was strongly associated with an increase in lifespan, and while it decreased risk of death from some causes, such as infectious disease, it actually increased risk of death from others, such as cancer. These findings suggest that to understand how reproduction affects lifespan, a shift in research focus is needed. Beyond the impact of reproduction on when individuals die, we must investigate its impact on why individuals die, and subsequently must identify the mechanisms by which these causes of death are influenced by the physiology associated with reproductive capability. Such an approach may also clarify the effects of reproduction on lifespan in people.
Tags: Scientific Results, The Science We Stand On