A cross-sectional study into the prevalence and conformational risk factors of BOAS across fourteen brachycephalic dog breeds.
Level 5 - mechanism / opinion, no new human data
Veterinary cross-sectional study (animal research).
PubMed 41706647 · doi:10.1371/journal.pone.0340604
What was done
Researchers adapted the respiratory functional grading (RFG) assessment to evaluate the prevalence and severity of Brachycephalic Obstructive Airway Syndrome (BOAS) in 898 dogs across 14 brachycephalic breeds in the UK pet population (Affenpinscher, Boston Terrier, Boxer, Cavalier King Charles Spaniel, Chihuahua, Dogue de Bordeaux, Griffon Bruxellois, Japanese Chin, King Charles Spaniel, Maltese, Pekingese, Pomeranian, Shih Tzu, and Staffordshire Bull Terrier). Conformational parameters were measured, and statistical analyses (comparative, within-breed, and multiple logistic regression) were performed to evaluate associations with BOAS status.
What was found
Almost every breed evaluated exhibited detectable breathing abnormalities. Only the Maltese and Pomeranian had no dogs with clinically significant BOAS. The Pekingese and Japanese Chin had the highest BOAS rates, with only 10.9% and 17.4% graded as unaffected (Grade 0), respectively. Across the entire sample, higher body condition score, nostril stenosis, and lower craniofacial ratio (more extreme facial hypoplasia) were significantly correlated with BOAS, accounting for 20% of the variation in disease status in multiple logistic regression. Some flat-faced breeds, such as the King Charles Spaniel, had lower BOAS rates than expected based on conformation.
Why it matters
This study expands BOAS characterization beyond the commonly studied Bulldog, French Bulldog, and Pug to 14 additional breeds. It demonstrates that while obesity, nostril stenosis, and extreme brachycephaly are shared risk factors, disease prevalence varies substantially by breed, supporting breed-specific prevention strategies.
Limits
The study is cross-sectional and observational, preventing causal inference. Measured risk factors explained only 20% of the variance in BOAS status, leaving most variation unaccounted for. The abstract does not report specific sample sizes per breed, odds ratios, or confidence intervals.