Researchers at the University of Cambridge have published research showing that Brachycephalic Obstructive Airway Syndrome (BOAS) prevalence and severity vary markedly between brachycephalic breeds, with Pekingese and Japanese Chins among the most affected¹.

The cross-sectional study, published in PLOS One, evaluated 898 dogs across 14 breeds and assessed conformational risk factors associated with BOAS.

Only 11% of Pekingese were graded free of BOAS.

Japanese Chins also showed high levels of disease, with only 17.4% graded unaffected.

King Charles Spaniels, Shih Tzus and Boston Terriers demonstrated intermediate risk profiles.

Cavalier King Charles Spaniels, Pomeranians, Boxers and Chihuahuas had substantially lower proportions of clinically affected dogs.

Across all breeds, increased facial shortening, dynamic nostril collapse and higher body condition score were significantly associated with BOAS severity.

Francesca Tomlinson, lead author and PhD researcher at the University of Cambridge, said: “Our research shows that BOAS varies widely between brachycephalic breeds.

"By understanding these differences and identifying key risk factors, we can move towards more targeted and effective strategies to improve welfare.”

The findings provide updated comparative data for clinicians advising owners on risk, weight management and early respiratory grading, and support structured respiratory grading schemes, including those led by The Royal Kennel Club.

References

• Tomlinson F. et al. (2026). A cross-sectional study into the prevalence and conformational risk factors of BOAS across fourteen brachycephalic dog breeds. PLOS One. Published 18 February 2026. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0340604 
   

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