Delayed spaying reduces risks of urinary incontinence in female dogs


A new study by the Royal Veterinary College (RVC) reveals that delaying the spaying of female dogs until they are between seven and 18 months old can reduce the risk of early-onset urinary incontinence by 20 percent compared to spaying at three to six months.

In the UK, three-quarters of all female dogs are spayed. While spaying can offer benefits both in terms of health and behaviour, it also has some disadvantages. Notably, there is an increased risk of urinary incontinence, which is leaking urine while lying down, after spaying.

Urinary incontinence affects one in thirty female dogs in the UK, with spayed dogs over three times more likely to become incontinent. This condition can be harmful to the welfare of affected dogs due to an increased risk of urinary tract infections and skin sores from urine-soaked skin. Until now, there has been some evidence linking the age at which a dog is spayed to the likelihood of developing urinary incontinence.

“Spaying is something that every owner will need to consider at some stage and so the findings of this study can feed into spay decision-making”

However, most previous studies only reported associations rather than proving a causal link between the age of spaying and urinary incontinence.

To address this gap, the RVC’s VetCompass Programme conducted a study using anonymised veterinary clinical records from over 30,000 female dogs born from 2010 to 2012 under first-opinion veterinary care in the UK. This study is notable for being the first to apply a new research method called veterinary causal inference. This method uses anonymised electronic clinical records to emulate a randomised controlled trial without requiring live animal participation.

The study analysed data from a random sample of 1,500 female dogs to replicate a randomised clinical trial. This allowed researchers to explore the impact of delaying spaying from 3-6 months to 7-18 months. The causal inference method created two mirrored groups of study animals, balanced for characteristics such as breed, veterinary group, and insurance status, enabling a comparison of urinary incontinence risk based solely on the age of spaying.

dog poo

The results demonstrated that spaying between seven and 18 months led to a 20 percent reduction in the risk of early-onset urinary incontinence compared to spaying between three and six months.

Camilla Pegram, VetCompass PhD student 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 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, added, “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.”


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