Brachycephalic Dogs and Breathing: New Research Shows BOAS Is More Than Just a "French Bulldog Problem"

by Steve Mehler, DVM, DACVS

For years, when veterinarians discussed Brachycephalic Obstructive Airway Syndrome (BOAS), the conversation almost always centered on three breeds: French Bulldogs, Bulldogs, and Pugs.

But a major 2026 study from researchers at the University of Cambridge has expanded our understanding dramatically. After evaluating nearly 900 dogs across 14 additional brachycephalic breeds, the authors found that breathing abnormalities are far more widespread than previously appreciated—and that each breed carries its own unique risk profile.

This research changes how veterinarians, breeders, and owners should think about airway disease.

What Is BOAS?

Brachycephalic Obstructive Airway Syndrome is a collection of anatomical abnormalities that make breathing more difficult.

These dogs aren't simply "snoring."

They are often breathing through narrowed airways every minute of every day.

Common consequences include:

• Chronic noisy breathing

• Reduced exercise tolerance

• Poor heat tolerance

• Difficulty sleeping

• Increased work of breathing

• Collapse during excitement or hot weather

• Reduced quality of life

In severe cases, BOAS can become life-threatening.

The Largest Multi-Breed BOAS Study to Date

Researchers evaluated 898 client-owned dogs from fourteen brachycephalic breeds using a standardized respiratory grading system developed by the University of Cambridge.

The breeds included:

• Affenpinscher

• Boston Terrier

• Boxer

• Cavalier King Charles Spaniel

• Chihuahua

• Dogue de Bordeaux

• Griffon Bruxellois

• Japanese Chin

• King Charles Spaniel

• Maltese

• Pekingese

• Pomeranian

• Shih Tzu

• Staffordshire Bull Terrier

Each dog underwent:

• Physical examination

• Respiratory grading before and after exercise

• Airway assessment

• Body condition scoring

• Skull and facial measurements

• Nostril evaluation

Dogs with previous BOAS surgery were excluded so the results reflected natural disease prevalence.

The Biggest Surprise

Almost every breed studied showed measurable breathing abnormalities.

Only two breeds—Maltese and Pomeranians—had no dogs with clinically significant BOAS in this study. That means airway disease extends well beyond the classic "flat-faced" breeds most veterinarians think about.

Which Breeds Were Highest Risk?

The study identified two breeds with BOAS prevalence comparable to Pugs and Bulldogs:

• Pekingese 

• Japanese Chin 

Only:

• 10.9% of Pekingese 

• 17.4% of Japanese Chins 

were completely unaffected (Grade 0).

Moderate-Risk Breeds

Several breeds had moderate rates of clinically significant disease:

• Boston Terrier

• Griffon Bruxellois

• Dogue de Bordeaux

• King Charles Spaniel

• Shih Tzu

Many owners of these breeds may assume noisy breathing is "normal."

The study suggests otherwise.

Lower-Risk Doesn't Mean No Risk

Breeds with lower overall prevalence still included affected individuals.

These included:

• Boxer

• Chihuahua

• Cavalier King Charles Spaniel

• Staffordshire Bull Terrier

• Affenpinscher

Even if a breed has lower average risk, individual dogs may still suffer significant airway obstruction.

What Actually Increased BOAS Risk?

Across all breeds, three factors consistently predicted disease.

1. Higher Body Condition Score

Overweight dogs had approximately 1.8 times greater odds of BOAS.

Fat around the neck and chest increases the work of breathing and reduces airway efficiency.

This is encouraging because body weight is one of the few risk factors owners can actively change.

2. Narrow Nostrils

Dogs with moderate nostril narrowing had over four times greater odds of BOAS.

Dogs with severe nostril narrowing had approximately ten times greater odds.

Tiny nostrils dramatically increase resistance before air even reaches the throat.

3. Shorter Muzzles

Researchers measured something called the craniofacial ratio (CFR)—essentially how much muzzle length exists relative to skull length.

Lower ratios (shorter muzzles) were associated with higher BOAS risk across the population.

However, the relationship was not identical between breeds.

Flat Face Doesn't Tell the Whole Story

One of the most fascinating findings was that facial shape alone does not explain everything.

Some breeds with extremely short faces had lower BOAS rates than expected.

For example, the King Charles Spaniel showed lower disease prevalence despite having a very low craniofacial ratio.

This suggests genetics, airway anatomy, and breed-specific traits all influence disease—not simply muzzle length.

Why This Matters

For years, discussions about BOAS often implied:

"Flat face equals airway disease."

This paper shows the picture is far more nuanced.

Instead, veterinarians should evaluate:

• Body condition

• Nostril size

• Breed-specific anatomy

• Exercise tolerance

• Clinical breathing sounds

rather than relying on appearance alone.

What Owners Should Watch For

If your dog is brachycephalic, talk with your veterinarian if you notice:

• Loud snoring while awake

• Exercise intolerance

• Frequent panting

• Sleeping with the neck extended

• Heat intolerance

• Gagging or retching after activity

• Cyanosis (blue gums)

• Episodes of collapse

These signs are not "cute."

They may indicate chronic airway obstruction.

Can BOAS Be Improved?

Yes.

Many affected dogs benefit from:

• Weight reduction

• Exercise management

• Avoiding overheating

• Early veterinary evaluation

• Surgical correction of stenotic nostrils and elongated soft palate when appropriate

Earlier intervention often leads to better long-term outcomes than waiting until severe respiratory compromise develops.

This landmark study reminds us that BOAS is not confined to French Bulldogs, Bulldogs, and Pugs. Breathing problems occur across many brachycephalic breeds, but the risk varies considerably from one breed to another. While shorter muzzles and narrow nostrils increase risk, maintaining a healthy body weight is one factor owners can directly influence. Most importantly, noisy breathing should never be dismissed as "normal for the breed." It is often a sign that the airway is working much harder than it should. As veterinarians, our goal should be to help dogs breathe comfortably—not simply accept abnormal breathing as part of their breed standard.