Which Dogs Are More Likely To Have Cushing’s Syndrome?
Which breeds are more likely to develop Cushing’s syndrome? Are female dogs more or less likely to develop Cushing’s? What about heavier or under-weight dogs?
Likelihood of Cushing’s in General–Prevalence and Incidence
A large-scale, nationwide (United Kingdom) study, conducted by researchers at the UK’s Royal Veterinary College and published in 2021 in the Journal of Small Animal Practice sheds light on these characteristics and others. The study measured the likelihood of a dog being diagnosed with Cushing’s over the course of a single year (one-year prevalence). The researchers used a UK national electronic repository of primary-care veterinary practice records covering the calendar year 2016. Within those records (covering 905,544 dogs, 1,527 of which were diagnosed Cushing’s dogs), the researchers determined that about 0.17% of dogs under veterinary care at any given time had Cushing’s syndrome. Included within that number, about 0.06% of dogs under veterinary care were newly diagnosed with Cushing’s during that year.
This was the first published report of incidence over the course of a one-year period across a large sample size of veterinary practices, so this is important information for veterinarians in determining if they are missing Cushing’s cases (if, for example, their practices are treating or diagnosing significantly fewer dogs than those benchmarks would suggest) and for dog owners in understanding how (un-)common Cushing’s syndrome is.
Which Breeds Are More Susceptible?
Using this large data set, the researchers were also able to identify several characteristics that made Cushing’s more or less likely. One important characteristic they found was breed. The breeds most likely to have Cushing’s syndrome were:
- Border terrier;
- Bishon frise; and
- Miniature schnauzer.
Other breeds with (statistically-significant) elevated odds of developing Cushing’s were:
- Lhasa apso;
- West Highland white terrier;
- Yorkshire terrier;
- Jack Russell terrier; and
- Staffordshire bull terrier.
The breeds that were least likely to have Cushing’s syndrome were:
- Golden retriever; and
- Labrador retriever.
Other breeds with lower odds of developing Cushing’s syndrome were:
- Border Collie; and
- Cocker spaniel.
The remaining breeds possessed average odds of developing Cushing’s or failed to possess enough cases to achieve statistical significance, although some studied breeds either developed no cases or only a couple of cases despite being well-represented. For example, of the 21,238 German shepherd dogs included within the study, none was diagnosed with Cushings. In addition, large numbers (ranging from 6,147 to 36,671 per breed) of Pomeranians, French bulldogs, Pugs, Cockapoos and Chihuahuas were included in the sample and each of those breeds had only one case of Cushings. Nonetheless, the number of Cushing’s cases in each of those breeds was too low to draw statistically-meaningful conclusions in this study.
This study appears to have been the first to identify the Border terrier, Lhasa apso and Stafordshire Bull terrier breeds as being especially susceptible to Cushing’s syndrome. This is especially surprising in the case of the Border terrier given that Border terriers had the highest prevalence of Cushing’s in the study population (with 1.02% of Border terriers being diagnosed with Cushing’s syndrome).
We note that other studies have shown Dachshund to be more susceptible to Cushing’s syndrome. However, that breed was not well-enough represented in this study to draw any conclusions about it.
Weight
Larger dogs (more than 30 pounds) seemed to have lower risk of Cushing’s syndrome (although that finding is only partially statistically-significant). This is because larger breeds are generally less susceptible to Cushing’s than smaller breeds, as is confirmed by the lists of breeds in the high and low-risk categories above. When controlling for breed and sex, dogs within any breed that were overweight, relative to their breed and sex, were more likely to be diagnosed with Cushing’s.
Sex
One surprising (to us, at least) finding was that female dogs are no more likely than male dogs to develop Cushing’s syndrome. Both prior research findings and our impressions formed from conversations with veterinarians and customers suggest that females were more likely to develop Cushing’s syndrome. This study failed (although only barely) to find a statistically-significant link between sex and likelihood of Cushing’s.
In its initial analysis, the study suggested that neutered dogs were more likely to have Cushing’s than entire dogs. However, in further analyses, the researchers determined that this effect was entirely accounted for by the other variables in their analysis (in particular, age and insurance).
Survival Time
The study found that the likelihood of diagnosis rises at an exponential rate as dogs age, especially within the first 7 years of life. The median age of diagnosis was 10.9 years.
After diagnosis, median survival time was about 1.5 years (594 days), with 10.4% of dogs surviving beyond the study period of 4.5 years of survival. However, 8.6% of Cushing’s dogs in the study received no treatment for the syndrome, so the expected survival time for dogs receiving treatment would be longer than those numbers suggest. This relatively long survival period “reflects a considerable amount of time for dogs to be living with Cushing’s syndrome and highlights the need to reduce the impact of the associated clinical signs and improve their quality-of-life during this time”. (Schofield at 271.) Many of our other posts address the special care needs of Cushing’s dogs, including diet, water, exercise, environmental conditions and skin and hair care.
Other Things That Caught Our Attention
Insured dogs were (much) more likely to be diagnosed with Cushing’s syndrome. Insurance does not cause Cushing’s syndrome! However, it is likely that those with insurance are more likely to seek diagnosis and treatment than those without. This would imply that a lot of Cushing’s cases are being missed and that the real world prevalence (vs those under veterinary care) is likely greater than that suggested by this study.
Concluding Thoughts
Cushing’s syndrome is not a common condition for most dogs. However, if your dog exhibits one or more signs of Cushing’s syndrome (the main ones of which are excessive thirst, excessive urination, excessive eating, hair or skin conditions, reduced activity, excessive panting and enlarged abdomen) and is older, or has greater body weight than the norm for its sex and breed, or is one of the higher risk breeds described above, then you and your veterinarian should consider a Cushing’s diagnosis and treatment. With proper treatment and attention to its special needs, your dog can still live comfortably for a long time.