Ask a room how long a dog lives and you get a shrug and a range. Eight years? Fifteen? Both answers are correct, which is the problem, because “dog” covers an animal that can weigh six pounds or 160.
In 2024, researchers published an analysis in Scientific Reports that narrowed the guess considerably. They pulled records on nearly 600,000 dogs across 155 breeds and looked for the traits that actually track with how long a dog lives. Two came out on top. One of them is size, which everyone already suspected. The other is the shape of the dog’s face, which is not a fact of nature. It is a design decision, made by humans, and we are still making it.
Size: the part we already knew
Across the animal kingdom, within a species, bigger usually means shorter-lived. It is true in humans. It is emphatically true in dogs.
The 2024 data backs it up, though less dramatically than people expect. Small dogs averaged 12.7 years. Large dogs averaged 11.9. Less than a year apart.
The averages hide the real story, which is variance. The Lancashire Heeler averaged 15.4 years. The Caucasian Shepherd Dog averaged 5.4. That is not a gap; that is a different animal. Small breeds like Shih Tzus, Chihuahuas, Dachshunds, and Toy Poodles routinely reach their teens, and some push into their early twenties. Mastiffs, Great Danes, Saint Bernards, and Great Pyrenees more typically land somewhere between six and twelve.
So size matters. It just is not the headline.
The muzzle: the part we built
Flat-faced, or brachycephalic, dogs are already known to be walking medical bills, and the airway is the reason.
The standard clinical picture is pinched nostrils plus an overlong stretch of soft tissue at the back of the throat, and it is worth sitting with what that actually means minute to minute. Air enters through an opening that is too narrow. It then hits a second blockage further in. The dog has to work to do a thing every other dog does without noticing. That constant work is what drives the associated heat-stroke risk, the heart problems, and the rest of the list.
The lifespans follow. In the study, flat-faced dogs averaged 11.2 years. Medium-muzzled dogs averaged 12.8 and long-muzzled dogs 12.1.
Now stack the two traits. Small dogs with long noses did best: Dachshunds and Whippets both averaged 13.3 years. Large flat-faced dogs did worst: Boxers and Bullmastiffs averaged 10.7. Two and a half years, gone, between one end of that combination and the other.
And there are exceptions, which is a useful reminder not to over-read any single trait. The Tibetan Spaniel is flat-faced and posted the second-longest average lifespan of any breed in the dataset, at 15.2 years.
“Size is the hand you were dealt, and face shape is the hand somebody dealt on purpose,” says Dr. Mara Chen. “That is why this study lands differently than a normal longevity paper. It is not describing dogs. It is describing what we did to dogs, and the bill for it comes due in years.”
What the study cannot tell you
The authors are candid about the limits, and they are worth knowing before you argue with anyone about this at the dog park.
It is a UK dataset. Breeding practices and ownership practices vary by country. The numbers may not port cleanly to the US.
It leans on insured and veterinary records, which skews the sample. Not every owner insures a dog, and some policies exclude older dogs or cost more for flat-faced breeds with known disease risk. Purebred dogs are also likely overrepresented in veterinary datasets, because, as one of the study’s authors noted, owners of purebreds have been shown to spend more on their dogs and to be more willing to pursue extensive treatment at referral hospitals.
Mixed-breed dogs got lumped together. The breakdown by breed only covered purebreds; every mixed-breed dog landed in a single bucket. So you cannot compare a small long-nosed mutt to a small long-nosed purebred, which is a shame, because prior research has found mixed-breed dogs are often hardier: fewer knee problems, less of certain cancers, less heart disease, less of several other conditions that end lives early.
What newer research adds
The paper picked up a formal author correction after publication, which is worth knowing if you go read the original: some of the figures were amended, and the version of record is the corrected one. The headline findings survived intact.
The broader shift since then has been away from breed as the interesting variable. Large longevity projects tracking tens of thousands of dogs keep finding that the things that move an individual dog’s lifespan the most are the boring, modifiable ones: staying lean, staying active, dental care, and not being socially isolated. Body size and skull shape set the range you are working in. Almost everything inside that range is yours.
Which is the useful way to hold this study. It is not a reason to feel doomed about the dog you have. It is a reason to think hard before you buy the next one.
So what do you do with this
If you already love a flat-faced dog, none of this is a verdict on them. It is a heads-up on what to watch: breathing effort at rest, heat intolerance, snoring that gets worse, exercise that stops early. Talk to your vet about airway surgery earlier rather than later if it is on the table, and be ruthless about weight, because every extra pound lands on an airway that was already struggling.
If you are choosing a dog, this is the part the breeder will not lead with. Ask what the breed’s typical lifespan is, and ask what it dies of. Prepare for the health problems that come standard.
And if you want a flat-faced dog anyway, which is a legitimate thing to want, adopt one instead of buying one. There is no shortage. The demand is what keeps the shape in production.
References
- McMillan, K.M., Bielby, J., Williams, C.L., Upjohn, M.M., Casey, R.A., and Christley, R.M. “Longevity of companion dog breeds: those at risk from early death.” Scientific Reports, 2024. https://www.nature.com/articles/s41598-023-50458-w
- “Author Correction: Longevity of companion dog breeds: those at risk from early death.” Scientific Reports, 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11021557/
- Bellumori, T.P., Famula, T.R., Bannasch, D.L., Belanger, J.M., and Oberbauer, A.M. “Prevalence of inherited disorders among mixed-breed and purebred dogs.” Journal of the American Veterinary Medical Association, 2013. https://pubmed.ncbi.nlm.nih.gov/23683021/
- Packer, R.M.A., Hendricks, A., Tivers, M.S., and Burn, C.C. “Impact of Facial Conformation on Canine Health: Brachycephalic Obstructive Airway Syndrome.” PLOS ONE, 2015. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137496
