Spayed female dogs at higher risk of brain tumors

In a novel study using canine brain scans, scientists have reported that spayed females had an increased relative risk of brain tumors — 11 times that of intact females. The authors cited the importance of estrogen to brain health, and related their work in dogs to findings in women regarding higher incidence of dementia than in men. Interestingly, intact female dogs were seven times less likely to get brain tumors than intact males, illustrating the significant protective impact of natural hormones on brain health in females.

The groundbreaking work was completed at the Royal School of Veterinary Studies Hospital for Small Animals at the University of Edinburgh. Almost 300 canine MRI brain scans were included in the study, with representation from 61 UK Kennel Club breeds as well as mixed breeds.  The scientists had to consider a wide variety of brain characteristics in dogs, given the extreme size differences and skull shapes. A number of factors were important to the incidence of brain abnormalities, including age. The concept of “brain age” has been receiving attention, and indicates the structural characteristics of the brain that are normally related to aging. This physiological brain age predicts disease risk better than chronological age.

In addition to showing for the first time that lack of natural hormones was related to brain aging and tumor development in female dogs, the authors also found that the boxer breed had an overall increased risk of premature “brain aging” and tumor development. Read the full article.

Over time, evidence has increased regarding the negative health impacts of hormone loss with spay and neuter in dogs (see our page on Hormone-Sparing Spay). This study is another reason why people should consider alternatives to spaying their female dogs (especially boxers).


Linda Brent, PhD

Executive Director, Parsemus Foundation

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