New research into BOAS: time for a fairer picture

In February 2026, a scientific study by the University of Cambridge (Tomlinson et al., PLOS One) was published regarding the presence of BOAS (Brachycephalic Obstructive Airway Syndrome) in fourteen dog breeds.

In this study, nearly 900 dogs were clinically assessed using the Respiratory Function Grading, a practical respiratory test (RFG). This assesses breath sounds and exercise tolerance. Consequently, it is not the dog's appearance that is evaluated, but its actual breathing.

This is an important difference from the widely used Craniofacial Ratio, a physical measure (CFR) used as an assessment tool within the policy rule for brachycephalic dogs. This measure is based solely on external characteristics, such as muzzle length, and says nothing about how a dog actually breathes or functions.

The Cambridge study specifically shows that respiratory problems cannot be reliably predicted based on skull proportions alone. This research thus underscores that an assessment based on function – such as with the respiratory test – provides a much more realistic and honest picture of the dog's health.

What does the research show?

The results provide a clear and nuanced picture: Many brachycephalic dogs are clinically healthy and do not exhibit BOAS. The severity of BOAS varies significantly by breed. External characteristics do play a role, but appear to explain only a limited part of the whole.

Important insight: external characteristics explain only ±20% of BOAS

The research shows that factors such as snout length, nasal opening, and body condition together explain only about 20% of the variation in BOAS. This means that the vast majority of differences in breathing – approximately 80% – cannot easily be traced back to what we see on the outside.

In other words: two dogs with a similar appearance can have completely different respiratory functions. It underscores that health cannot be reliably predicted based on external characteristics alone.

What does this mean?

This study confirms what has long been visible in practice: breathing in dogs is complex and cannot be determined from appearance alone. The breathing test from the Cambridge study therefore provides a fairer and more reliable picture of a dog's health than rules that look exclusively at skull proportions.

Time for policy based on objective, functional assessment of health

The findings of this study also raise a fundamental policy question. If it has been scientifically demonstrated that external characteristics explain only a limited proportion of respiratory problems, the question is to what extent policy based exclusively on these characteristics – such as the current external measure within the policy rule for brachycephalic dogs – is still appropriate and effective.

A system that assesses dogs based on their appearance but not on how they actually function runs the risk of: unfairly excluding healthy dogs. And at the same time, offering no guarantee that respiratory problems are actually addressed. This research shows that a shift is needed towards an objective, functional assessment of health, such as with the respiratory test. Only by measuring what truly matters—breathing itself—can policy effectively contribute to improving animal welfare.

The way forward

The good news is that respiratory problems can be modified.

By breeding dogs that score well on objective respiratory tests, the health of future generations can be further improved.

This calls for an approach based on:

• Measuring what really matters (function)

• An open and honest picture, without prejudice

• Collaboration between breeders, veterinarians, and interest groups

  
  

Conclusion

The Cambridge study shows that many short-snouted dogs are healthy and that a fair assessment begins with what a dog can do – not with how it looks.

Source / report: Tomlinson F. et al. (2026) – A cross-sectional study into the prevalence and conformational risk factors of BOAS across fourteen brachycephalic dog breeds: https:// journals.plos.org/plosone/article?id=10.1371/journal.pone.0300000