University of Cambridge researchers have identified 12 dog breeds at increased risk of a breathing disorder long associated mainly with pugs and French bulldogs. The study, which assessed nearly 900 dogs across 14 brachycephalic breeds, found that breeds ranging from Pekingese to Staffordshire bull terriers showed measurable rates of brachycephalic obstructive airway syndrome, or BOAS. The findings challenge a widespread assumption that only the most extremely flat-faced dogs are affected, and the researchers say the results could inform breeding standards, veterinary screening, and decisions by prospective dog owners.
Twelve Breeds, Not Three, Show Clinical Signs
Previous BOAS research concentrated on the three most popular flat-faced breeds in the United Kingdom: the French bulldog, the pug, and the English bulldog. The new cross-sectional study, published in PLOS ONE, deliberately widened that lens. Researchers examined a dataset of approximately 898 dogs spanning 14 brachycephalic breeds, grading each animal on a clinical scale from 0 (no signs) to 3 (severe). Of those 14 breeds, 12 showed detectable clinical signs of BOAS, meaning the problem extends well beyond the usual suspects.
The affected breeds include Shih Tzu, Cavalier King Charles spaniel, chihuahua, boxer, and Japanese Chin, according to University of Cambridge reporting on the results. That list is likely to surprise owners who consider some of these breeds relatively healthy. Staffordshire bull terriers, for instance, are muscular, athletic dogs not typically grouped with flat-faced lapdogs, yet the data showed they too carry measurable BOAS risk. The breadth of breeds involved suggests the condition is driven by a cluster of physical traits rather than a single extreme skull shape.
Pekingese and Japanese Chin Face the Steepest Odds
Among the 14 breeds, Pekingese dogs fared worst. Only about 11% of Pekingese in the study were free of any BOAS symptoms, according to the PLOS summary of the findings. Japanese Chin were close behind, with approximately 17.4% scoring symptom-free. Those figures mean that roughly nine out of every ten Pekingese examined showed at least some degree of breathing compromise, a rate that should prompt hard questions about current breed standards for these dogs.
What makes these numbers especially striking is that many owners may not recognize mild BOAS in their pets. Dogs graded at level 1 on the clinical scale can appear outwardly normal while still experiencing restricted airflow, noisy breathing during sleep, or reduced exercise tolerance. The grading system the Cambridge team used, adapted from the internationally recognized Respiratory Function Grading Scheme, was specifically calibrated for breeds that had never been formally assessed before. That adaptation is itself a significant step, because it means veterinarians now have a standardized tool to evaluate BOAS across a much wider range of dogs.
Physical Traits That Predict Breathing Trouble
The study went beyond simple breed-level prevalence rates. Researchers measured a suite of conformational features in each dog, including craniofacial ratio (how flat the face is relative to the skull), nostril narrowing and collapse, body condition, neck thickening, and tail length. These measurements allowed the team to identify which specific physical characteristics correlate with worse BOAS outcomes. Flatter faces and narrower nostrils were predictable risk factors, but the data also pointed to shorter tails as a correlate for the syndrome in some breeds. Tail length may seem unrelated to breathing, but the researchers reported an association between shorter tails and BOAS in some breeds, adding to evidence that multiple physical traits can track with airway risk.
A separate but complementary study published in The Veterinary Journal used CT imaging to map upper-airway lesions from the nostrils to the cervical trachea and linked those lesions to a BOAS severity index. Together, the two studies offer both a functional picture (how well the dog breathes) and an anatomical one (what is physically obstructed). That dual evidence base gives breeders and regulators a clearer target: rather than relying on subjective visual assessments, they can now point to measurable traits that predict clinical disease.
Why Wider Screening Could Change Breeding Decisions
Most coverage of brachycephalic health problems focuses on surgery, the corrective procedures that widen nostrils or trim excess soft palate tissue. But the Cambridge findings argue for a shift upstream, toward prevention through breeding choices. If BOAS prevalence and severity vary widely by breed, as the cross-sectional data demonstrate, then routine health screening at dog shows and breeding evaluations could identify high-risk animals before they reproduce. Dogs were assessed not only at the Queen’s Veterinary School Hospital but also at dog shows and health testing days, showing that the grading protocol works outside a clinical setting.
One gap in the current evidence is the absence of official responses from breed clubs or kennel organizations. The study calls for action, but whether registries will incorporate BOAS grading into their breeding requirements remains an open question. Without institutional buy-in, individual breeders may feel pressured to prioritize appearance over function. However, if kennel clubs begin to require respiratory grading or reward dogs with healthier airway scores in the show ring, that could rapidly shift incentives toward less extreme conformations and lower BOAS risk across entire populations.
What the Study Means for Owners, Vets, and Future Research
For current and prospective owners, the message is not that all flat-faced dogs are doomed, but that vigilance is essential across a wider range of breeds than previously assumed. Owners of Pekingese, Japanese Chin, Shih Tzu, and other identified breeds should treat noisy breathing, snoring, exercise intolerance, or heat sensitivity as potential clinical signs rather than quirks of the breed. Early veterinary assessment using standardized respiratory grading can help determine whether lifestyle adjustments, weight management, or in some cases surgery might improve quality of life. The work from Cambridge underscores that even dogs with mild symptoms may be experiencing chronic low-level distress that owners can easily overlook.
For veterinarians, the expanded grading scheme offers a practical tool to bring into consultations, puppy health checks, and pre-breeding evaluations. Clinics that participate in structured research or surveillance programs can also contribute data that helps refine risk estimates over time and improves how BOAS is identified across breeds.
The communication strategy around studies like this also matters. Open-access outlets and science press offices play a key role in translating technical work into language that non-specialists can act on. The Cambridge BOAS research reached a broad audience through institutional briefings and coverage coordinated via platforms such as the PLOS media resources page and independent services like EurekAlert, which help journalists locate peer-reviewed evidence quickly. As more data accumulate on how skull shape, tail length, and other traits interact to drive BOAS risk, clear, accessible reporting will be vital to support evidence-based reforms in breed standards and to help families choose dogs that can breathe freely throughout their lives.
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*This article was researched with the help of AI, with human editors creating the final content.
