The Canine Ledger

Choosing a Breed or a Mix: The Health Data Breeders Don't Lead With

UK vet records show some breeds carry far more disease than others, and that a mix isn't automatically healthier. What the data say before you choose.

Written by thecanineledger

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In a study of UK dogs who died between 2016 and 2020, the average life expectancy at birth was 11.23 years. For one popular breed it was far lower: “Jack Russell Terrier (12.72 years; 95% CI: 12.53-12.90) and French Bulldog (4.53 years; 95% CI: 4.14-5.01) had the longest and shortest life expectancy at age 0, respectively” (Teng et al., Sci Rep 2022).

A breed’s look, size and temperament are what most people choose on. Its health record is rarely what the seller leads with.

While no breed guarantees a healthy dog and no breed dooms one, the differences between breeds in vet records are large and consistent. This page explains what the main UK studies found, and how to use them when choosing.

1. Where the data come from

Most of the figures on this page come from VetCompass, a research programme at the Royal Veterinary College that studies anonymised records from UK vet practices. Because it uses records of dogs seen for any reason, not just referral cases, it gives a fair picture of everyday health.

Its limits: it covers the UK only, it counts what vets recorded, and younger breeds can look healthier simply because their dogs are younger.

Our note: The French Bulldog figure (4.53 years) comes from dogs that died in the study period. UK French Bulldogs were a young population then (O’Neill 2021 gives a median age of 1.51 years), which may pull the figure down.

2. Flat-faced breeds: the clearest evidence

Flat-faced (brachycephalic) dogs include French Bulldogs, Bulldogs and Pugs. A UK study of 22,333 dogs concluded that it “provides strong evidence that brachycephalic breeds are generally less healthy than their non-brachycephalic counterparts” (O’Neill et al., Sci Rep 2020).

A study of French Bulldogs compared 2,781 of them with 21,850 other dogs. French Bulldogs “had significantly increased adjusted odds of 20/43 (46.5 %) disorders” (O’Neill et al., Canine Med Genet 2021). The largest differences were in breathing and skin problems that come from their body shape. They had much higher odds of narrowed nostrils and of brachycephalic obstructive airway syndrome (BOAS), a breathing disorder caused by the short muzzle.

It wasn’t all one way. French Bulldogs had lower odds of 11 of the 43 disorders. But the authors concluded that the breed’s health “has diverged substantially from, and may be lower than, the health of the wider non-French Bulldog population,” and that “Many of these predispositions are closely associated with the conformational extremes that define the French Bulldog breed.”

→ Breathing Problems in Flat-Faced Dogs: What BOAS Is

3. Is a mix healthier?

The common belief is that mixed-breed dogs are healthier because of “hybrid vigour”. The evidence is more mixed than that.

A US study of 27,254 dogs with one of 24 inherited disorders found “No differences in expression of 13 genetic disorders” between purebred and mixed-breed dogs, including hip dysplasia and several cancers. Purebred dogs were more likely to have 10 disorders. Mixed-breed dogs were more likely to have one, a torn cruciate ligament in the knee (Bellumori et al., J Am Vet Med Assoc 2013).

So a mix can lower the risk of some breed-specific diseases, but it doesn’t remove inherited risk. The parents matter.

For flat-faced breeds, crossing toward a longer muzzle does seem to help. A 2026 UK study compared Pugs with Pug crosses and found that “Purebred Pugs exhibited a significantly higher prevalence of respiratory, ocular, dermatological and musculoskeletal disorders” than the crosses, which had longer muzzles and more open nostrils (Youens et al., Anim Welf 2026). This was a study of about 150 dogs, so the finding needs confirming.

Our note: The Bellumori 2013 abstract doesn’t say whose medical records it used. If they came from a referral hospital, they may not reflect dogs in general practice.

4. Size matters too

Breed isn’t the only factor. In UK vet records, smaller dogs had more dental disease: “Increasing adult bodyweight was associated with progressively decreasing odds of periodontal disease” (O’Neill et al., J Small Anim Pract 2021). → Dental Disease in Dogs: What Brushing Can and Can’t Do

Large and giant breeds have their own problems, including joint disease. Every type of dog has a health profile worth knowing.

Our note: We give no source on this page for joint disease risk in large and giant breeds.

5. How to use this when choosing

  • Look up the breed’s health problems before you fall for a puppy. Your vet can tell you what they see most in that breed.
  • Ask the breeder which health tests the parents have had for problems known in the breed, and ask to see the results.
  • For a flat-faced breed, ask about breathing. Does either parent snore, struggle in heat or tire quickly? Is there a breathing assessment for the breed where you live?
  • For a mix, ask about both parents. A cross of two breeds can carry the problems of either.
  • Think about the costs of a breed with known problems. → Vet Bills, Medicines and Decisions

Our note: The UK has a breathing grading scheme for flat-faced breeds, which we haven’t read. We don’t know of equivalents in Canada or the US.

6. What we could not verify

Commonly saidWhat we found
“Mixed breeds are always healthier”Not always. No difference for 13 of 24 inherited disorders in one US study.
“Snoring is normal for a flat-faced dog”Not covered by our sources in those words. Breathing disorders are much more common in these breeds.
“Kennel-club registration means a healthy dog”Not covered by our sources. Ask for the parents’ health test results instead.
Life expectancy for breeds in Canada and the USNot found. The figures here are UK only.

Sources

Always confirm with your vet before acting on anything on this page.