Later-age spaying of bitches reduces risk of urinary incontinence

A new study from the Royal Veterinary College (RVC) has revealed that delaying spaying of bitches until between seven and 18 months causes a 20 percent reduction in the risk of early-onset urinary incontinence, compared with early-age spaying between three and six months. The findings will help vets make evidence-based recommendations on the timing of spaying, whilst taking into account other spaying considerations.

Urinary incontinence affects one in thirty bitches in the UK, with spayed bitches over three times more likely to experience this affliction. The condition can be distressing and costly for owners and can also harm the welfare of affected dogs due to an increased risk of urinary tract infections and urine scald. Previous RVC VetCompass research identified that Irish setters, Dalmatians, Hungarian vizslas, Dobermans, Weimaraners, Shar-peis and Boxers are the breeds at greatest risk of early-onset urinary incontinence, with increasing body weight also resulting in increased incontinence risk. However, the evidence on the timing of spaying relative to urinary incontinence risk has, to date, been less definitive.

Additionally, while clinical trials are typically considered the gold standard for determining causal treatment effects, they are not always practical or ethical. Therefore, this study is now one in a series to use novel methods of causal inference "target trial emulation" to estimate real-world causal effects based on anonymised veterinary electronic clinical records. Causal inference from large databases can be viewed as an attempt to emulate a randomised controlled trial to answer a question of interest that often cannot be answered in any other way.

Conducting this study, researchers from the RVC’s VetCompass Programme, set out to research the impact of spaying on urinary incontinence in bitches, using the anonymised clinical records from more than 30,000 bitches under first-opinion veterinary care in the UK born from 2010 to 2012.

This included a random sample of 1,500 bitches spayed between three and 18 months. Of these, 612 (40.8%) bitches were spayed between three and six months and 888 (59.2%) at seven to 18 months. The analytic methods used in the study balanced the two groups of bitches across other characteristics including breed, veterinary group, insurance status and chronic illnesses. This meant that the only remaining difference between the two groups was when they were spayed.

The results showed that bitches spayed between seven and 18 months had 0.80 times the likelihood of developing early-onset urinary incontinence compared with bitches spayed between three and six months. This means the bitches spayed later had a 20 percent reduction in the risk of early-onset urinary incontinence.

Camilla Pegram, VetCompass PhD candidate at the RVC and lead author of the paper, said:

"This study is now one in a series using an exciting new approach, allowing us to determine ’cause’ rather than being limited to ’association’. Spaying is something that every owner and vet will need to consider at some stage and so the findings of this study can feed into spay decision-making. Although a decision to spay a bitch is based on many other factors other than urinary incontinence risk, the results suggest early-age spaying should be carefully considered and well justified."

Dr Dan O’Neill, Associate Professor in Companion Animal Epidemiology at the RVC and co-author of the paper, said:

"These new findings help vets and owners to rely more on evidence rather than opinion when making decisions about when to spay bitches. The new scientific methods of causal inference developed by the RVC for this research series are also contributing to reducing the need to use live animals to answer vital research questions."

Paula Boyden, Veterinary Director at Dogs Trust, said:

"Dogs Trust is delighted to have supported this evidence-based research which will lead to improved dog welfare. The study will help vets and dog owners make informed decisions about the best time to neuter a dog to reduce the risk and prevalence of urinary incontinence developing throughout their lifetime."

Infographic pdf is downloadable here.


Pegram, C., Diaz-Ordaz, K., Brodbelt, D. C., Chang, Y., Hall, J. L., Church, D. B. & O’neill D.G. 2024. Later-Age Neutering Causes Lower Risk Of Early-Onset Urinary Incontinence Than Early Neutering - A Vetcompass Target Trial Emulation Study. PLOS ONE.

The full paper is available from PLOS ONE and can be accessed here:­sone/artic­le’i­d=10.1371/­journal.po­ne.0305526
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About the RVC

  • The Royal Veterinary College (RVC) is the UK’s largest and longest established independent veterinary school and is a Member Institution of the University of London.
  • It is one of the few veterinary schools in the world that hold accreditations from the RCVS in the UK (with reciprocal recognition from the AVBC for Australasia, the VCI for Ireland and the SAVC for South Africa), the EAEVE in the EU, and the AVMA in the USA and Canada.
  • The RVC is ranked as the top veterinary school in the world in the QS World University Rankings by subject, 2024.
  • The RVC offers undergraduate and postgraduate programmes in veterinary medicine, veterinary nursing and biological sciences.
  • The RVC is a research-led institution, with 88% of its research rated as internationally excellent or world class in the Research Excellence Framework 2021.
  • The RVC provides animal owners and the veterinary profession with access to expert veterinary care and advice through its teaching hospitals and first opinion practices in London and Hertfordshire.

About the VetCompass? Programme

VetCompass? (The Veterinary Companion Animal Surveillance System) is an epidemiological research programme at the Royal Veterinary College (RVC) which investigates anonymised clinical records from veterinary practices to generate evidence to support improved animal welfare. VetCompass shares information from more than 1,800 veterinary practices in the UK (over 30% of all’UK practices) covering over 28 million companion and equine animals. To date, VetCompass? has led to over 120 peer-reviewed publications that have supported welfare-focused work across the range of animal stakeholders including the wider general public, owners, breeders, academics, animal charities, universities and government.

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