12 additional dog breeds confirmed at risk of serious airway obstruction

Brachycephalic Obstructive Airway Syndrome has long been associated with a short list of breeds: Pugs, French Bulldogs, English Bulldogs. These dogs dominate welfare discussions in part because their extreme skull compression is visible and their popularity is high. But a study from the Cambridge Veterinary School, published in PLOS ONE, extends that list considerably, confirming 12 additional breeds as facing meaningful BOAS risk - among them the Staffordshire Bull Terrier, Boston Terrier, Boxer, Cavalier King Charles Spaniel, Chihuahua, and Pekingese.

BOAS as a spectrum, not a binary

"BOAS exists on a spectrum. Some dogs are only mildly affected, but for those at the more severe end, it can significantly reduce quality of life and become a serious welfare issue," said a senior researcher on the study. The condition arises from the structural consequences of selecting for shortened skulls. Soft tissues including the soft palate, throat walls, and nasal turbinates do not shrink proportionally when the skull compresses front-to-back. Airway narrowing follows, producing everything from noisy breathing and disrupted sleep to exercise intolerance and surgical emergencies in severe cases.

The condition's severity varies both between breeds and within them. A mildly affected Staffordshire Bull Terrier may breathe normally at rest and show only minor stress during exercise, while a severely affected dog of the same breed may require intervention to prevent respiratory crises in warm weather. Understanding which physical features drive severity - rather than which breeds are affected as categories - offers more precise guidance for breeding decisions and veterinary assessment.

The body tells multiple stories

The Cambridge team found that skull dimensions alone do not determine BOAS risk. Three physical characteristics consistently predicted disease severity across breeds: head shape (shorter, wider relative to body size), nostril width (narrowed nostrils restrict airflow at the most upstream point), and body weight (overweight animals showed substantially worse scores). In some breeds, neck circumference and tail set - the latter correlating with spinal conformation - also contributed.

This multi-trait picture matters practically. A dog with a relatively flat face but wide nostrils and lean body condition may have far better airway function than a dog with a slightly less extreme skull but collapsed nostrils and excess weight. Veterinary assessments and breeder selection criteria benefit from considering the full physical profile rather than breed classification alone.

Breeds now confirmed to carry risk

The 12 breeds newly confirmed as at meaningful BOAS risk by the study include: Pekingese, Shih Tzu, Boston Terrier, Staffordshire Bull Terrier, Cavalier King Charles Spaniel, Chihuahua, Boxer, Japanese Chin, Pomeranian, King Charles Spaniel, Lhasa Apso, and French Bulldog crosses. Some of these - particularly the Chihuahua and Staffordshire Bull Terrier - may surprise owners who associate BOAS primarily with the most visibly flat-faced breeds. These breeds have shorter-than-average skulls relative to their overall body size even if they do not appear dramatically flat-faced.

Implications for breeding and ownership

The study's findings carry direct relevance for breeding practices. The significant within-breed variation in BOAS severity means that selective pressure toward less extreme conformation - wider nostrils, less compressed skull depth, leaner body condition - could reduce population-level disease burden even within high-risk breeds. The authors note that responsible breeders and breed clubs in several countries have begun incorporating BOAS screening into breeding recommendations, particularly following regulatory pressure in Scandinavia and the Netherlands.

For owners of affected breeds, the data reinforces several practical points. Maintaining healthy body weight is the single most modifiable risk factor, and the association between overweight status and worse BOAS scores was consistent across the dataset. Early veterinary assessment for BOAS - particularly before a dog is first bred from - gives the best chance of identifying animals whose airway function is poor enough to warrant intervention before symptoms become severe.

The study is based on dogs examined at veterinary and research facilities, which may not fully represent the breed populations at large. Dogs with severe symptoms are more likely to be presented for assessment, potentially inflating apparent disease rates. Population-based screening studies would give a clearer picture of true prevalence across each affected breed.