The breathing problem we bred into our favorite dogs — and how we might breed it out

Doges Editorial · 2026-05-23 · 6 min read

French bulldogs became America's most popular breed in 2022. A new Royal Kennel Club study in PLOS One shows the breathing disorder affecting roughly 1 in 5 of them is partly heritable — meaning selective breeding could genuinely reduce it.

If you have spent time with a French bulldog, you know the sound. A soft wheeze on the inhale. The clicking at the back of a pug's throat after a short run up the stairs. The way an English bulldog's breathing can be audible across a quiet room. These sounds have become so familiar that many owners assume they are simply part of the breed — charming, even, the way a sidecar changes the silhouette of a motorcycle. A study published May 13, 2026 in the open-access journal PLOS One makes the case that they are not inevitable, and that breeders have more power to reduce them than previously understood.

America's most popular dog can barely breathe

For more than thirty years, the Labrador retriever held the top spot in the American Kennel Club's breed rankings. In 2022, the French bulldog ended that streak. The Frenchie is now the most registered dog in the United States — compact, expressive, city-appropriate, and in enormous demand. It is also a breed in which roughly 15-20% of tested individuals show clinically meaningful signs of brachycephalic obstructive airway syndrome, or BOAS.

BOAS is what happens when a very flat face, narrowed nostrils, an elongated soft palate, and a compressed airway are bred together. The dog can breathe — but not easily. Exercise intolerance, sleep disruption, heat stress, and in severe cases, complete respiratory obstruction that requires surgery. Veterinarians and researchers have called the combination of rising BOAS rates and rising demand for affected breeds the 'brachycephalic crisis.' The question the new Royal Kennel Club study set out to answer is whether genetics gives us any way out.

What the researchers actually measured

Geneticists led by Dr. Joanna Jadwiga Ilska at the Royal Kennel Club analyzed breeding records and health-testing data from thousands of bulldogs, French bulldogs, and pugs registered with the Royal Kennel Club in the UK. They used the Respiratory Function Grading Scheme, a standardized exercise test that scores dogs on a four-point scale from fully unaffected to severely affected. Dogs were also scored on nostril size and body weight — two traits that correlate with BOAS severity.

Then they calculated heritability: what fraction of the variation in these traits between individual dogs can be attributed to genetic differences between them, rather than environment, age, or chance. Heritability doesn't tell you which genes are responsible. It tells you whether selection — choosing which dogs to breed from — can move the needle on a trait across generations. A heritability of zero means selection is useless. A heritability of 0.5 means half the variation is genetic and selection will produce meaningful change relatively quickly.

The results: respiratory function was 21 to 49 percent heritable depending on the breed. Nostril size was 31 to 39 percent heritable. Both estimates fall in the moderate range — high enough to make within-breed selection a viable strategy. And critically, the three traits — respiratory function, nostril size, and body weight — tended to cluster together. Dogs with narrow nostrils were more likely to be heavier and to grade worse on the respiratory test. That clustering is actually good news for breeders, because it means selecting against one trait tends to improve the others.

The key quote from the research team

Our findings provide clear evidence that respiratory health in these breeds is influenced by genetic differences between dogs, and importantly, that improvement is achievable through selective breeding. By using objective tools like the Respiratory Function Grading Scheme, breeders can make more informed decisions that prioritize health, helping to reduce the prevalence of BOAS over time.

— Dr. Joanna Ilska, Royal Kennel Club, in a statement accompanying the PLOS One publication

The emphasis on 'objective tools' matters. One persistent challenge in breed-health improvement is that informal assessments — an experienced eye, a breeders' intuition — are easily biased toward aesthetics. The Respiratory Function Grading Scheme provides a standardized exercise test score that travels across kennels and breeding programs. If more breeders used it, the data would accumulate, the selection would become informed, and over several generations the average breathing capacity in these breeds would shift.

Why we kept choosing the flattest faces anyway

The other half of the brachycephalic crisis is demand. French bulldogs went from niche novelty to most-registered breed while awareness of BOAS was rising, not falling. Understanding why requires a short detour into developmental psychology. The combination of features that define these breeds — short muzzle, tall forehead, relatively large eyes — closely mirrors the proportions of a human infant. Research on what biologists call 'neoteny' suggests that humans are evolutionarily primed to find baby-like faces compelling. The attachment response that evolved to keep us caring for vulnerable infants gets triggered by a pug.

This is not a flattering explanation, but it is a useful one. It suggests that demand for brachycephalic breeds is not going to evaporate through awareness campaigns alone — the pull is too deep and too automatic. The more realistic path is what the Ilska study describes: changing the genetics of the breeds themselves, from the inside, using breeders who understand what the data is telling them.

What this means for owners of flat-faced dogs today

The study's implications for current owners are practical rather than genetic. You can't change your dog's heritability. But you can manage how BOAS affects their daily life. The Royal Kennel Club's guidelines for BOAS management emphasize three levers: keeping dogs lean (excess weight compresses an already restricted airway), giving frequent rest breaks during exercise, and helping them stay cool in summer heat.

For flat-faced dogs, this means walks look different. Shorter loops rather than long sustained efforts. Early morning or evening timing in warm months, when pavement temperature drops and ambient heat doesn't push the respiratory system. Carrying water. Paying attention to the sound of their breathing as a real-time indicator rather than background noise. A bulldog who is wheezing harder than usual on a route they normally handle is telling you something specific about the conditions that day.

French Bulldogs had the lowest prevalence of BOAS in the study, at 15.6% of tested dogs, compared to 18.9% of Bulldogs and 19.8% of Pugs — rates the authors note may still be underestimates, since few flat-faced dogs are screened unless they show symptoms.

— Campbell et al., PLOS One, 2026 — different concurrent BOAS study

The longer game

Changing a breed's health profile through selective breeding takes a generation to see clearly and multiple generations to confirm. The Ilska study's contribution is not a fix — it is evidence that a fix is genetically possible, and a tool to pursue it. That distinction is important. Veterinarians and breed organizations have sometimes argued that BOAS is so structurally embedded in brachycephalic breeds that meaningful within-breed improvement was unrealistic. The heritability estimates in this study challenge that pessimism.

French bulldogs are not going anywhere. Their presence in cities, in apartments, in cafes and parks and TikTok videos is a settled fact of contemporary pet culture. The question is what the French bulldogs of 2036 will sound like — whether that familiar wheeze will be less common, less severe, a little quieter on the morning walk. The answer will depend on what breeders in the next few years choose to do with a grading scheme and a set of heritability numbers. The genetics, it turns out, are willing.

Improvement is achievable. The key is giving breeders objective information and the commitment to use it.

— Dr. Joanna Ilska, Royal Kennel Club, PLOS One May 2026