Mixed-Breeds vs. Purebreds: Are Mutts Healthier?




BY Sheila Pell
Marija Kovac / Stocksy
If you are considering adopting a dog, one important factor to consider is health. Mutts, or mixed breeds, boast a unique ancestry, combining two or more breeds and their diverse gene pool can act as a shield against hereditary diseases that might haunt some purebreds. It’s well known that some dog breeds are at higher risk for certain conditions, for example, hip dysplasia and Great Danes, Bulldogs and respiratory challenges, and Dachshunds with their spinal issues. So, when it comes to mutts versus purebreds, is it true that mixed breeds are healthier? There have been several studies on canine health that tilt the mutt versus purebred assumption — just a bit.
Are mixed breeds healthier?
There’s no doubt about it: Mixed breeds are generally healthier than purebred dogs because of their diverse genetic pool. Does that mean that all mixed-breed dogs are healthier than purebred dogs? No. Of course, any dog can get diseases and illnesses throughout their lives. But if you adopt a mutt from a reputable organization, treat them well and give them plenty of TLC, you have a good chance that they’ll live a long and healthy life.
On the other hand, purebred dogs have a limited gene pool, which means genetic disorders are more likely to be passed from one generation to the next. One study found that of 24 genetic disorders, it turns out that both mutts and purebreds shared a similar risk for 13 of them. Mixed breeds are at a higher risk for one disorder (ruptured cranial cruciate ligament). But the remaining 10 inherited conditions are more prevalent in purebred dogs.
Conditions more common in purebred dogs:

Aortic stenosis (narrowing above the aortic heart valve or of the valve)
Atopy / allergic dermatitis (skin allergies)
Gastric dilatation-volvulus (bloating and twisting of stomach)
Early onset cataracts (clouding of the lens inside the eye)
Dilated cardiomyopathy (enlargement of the heart chambers)
Elbow dysplasia (abnormal tissue growth that harms the joint)
Epilepsy (brain seizures)
Hypothyroidism (underproduction of thyroid hormones)
Intervertebral disk disease (IVDD affects the disks of the spine, causing neurological problems)
Hepatic portosystemic shunt (abnormal blood circulation around the liver rather than into it). 

And in another blow to purebreds, a study by Wisdom Panel found that purebred dogs were 2.8 times more likely than mixed breed dogs to have a recessive disease such as progressive retinal atrophy, hyperuricosuria, Collie eye anomaly, multidrug sensitivity, and von Willebrand’s disease — giving mixed-breed dogs the crown yet again. “This DNA-testing–based evidence shows that while mixed-breed dogs are in fact less likely than purebreds to develop the recessive disorders evaluated in the study, they may still be carriers,” says Dr. Cindy Cole, general manager at Wisdom Health, in a statement about the study.
Do mixed-breed dogs live longer?
Yep, research shows that mixed-breed dogs live longer than purebred dogs, with the median lifespan for a mixed-breed dog being 14.5 years. But body size and sex play a bigger role, with small dogs living longer than larger dogs and female dogs living significantly longer than male dogs. Neuter status also has some influence on lifespan: Intact males have shorter lives. And the breed group with the shortest lifespan? Working dogs.
Mutts vs. purebred groups
Rather than comparing the health of mixed-breed dogs and specific dog breeds, we can get some clarity here by looking at the differences between American Kennel Club (AKC) breed groups and mutts. Is a particular group of dogs prone to genetic disorders? According to a study, among the purebred groups, health differences were clear. Ultimately, the hardy terrier emerged as the top purebred group. Here’s a breakdown:

Terriers: Compared to mixed-breeds, terriers were more likely to have two disorders (skin allergies and portosystemic shunt) but were less likely to have intervertebral disk disease.
Herding: Herding dogs were more likely to have four conditions than mutts. Those conditions include aortic stenosis, elbow dysplasia, epilepsy, and IVDD.
Hounds: Hounds were at higher risk than mutts for four conditions, including dilated cardiomyopathy, epilepsy, hypothyroidism, and IVDD.
Non-sporting group: Ranging from Poodles to Dalmatians, these pups were more likely than mutts to have five disorders (allergies, bloat, cataracts, hypothyroidism, and IVDD).
Working breeds: For animals expected to have grit and vigor — they were prone to six more disorders! (They were at higher risk of all disorders except allergies, cataracts, and epilepsy).
Sporting group: Bred for outdoor stamina, these pups were the worst in health. They were more at risk for seven of the 10 inherited disorders.

So, do purebred dogs have more health problems?
While researchers found seven conditions where more than half of purebred groups were statistically neck and neck with mixed-breeds, most purebred groups had a much higher prevalence than the mixes for three other conditions: skin allergy, hypothyroidism, and IVDD. 
Aortic stenosis, a heart condition present at birth, was higher in dogs bred for endurance: herding, sporting, and working AKC groups. But, the researchers say the data “suggests that most breeds in the herding group are not at higher risk” — except the German Shepherd, which other studies have also found susceptible.
And while Retrievers were more affected by aortic stenosis, another sporting breed, the Spaniel, wasn’t. For a different malady, Spaniels were the unluckiest. Epilepsy was more prevalent in herding, hound, and sporting groups, particularly the Spaniel breeds. Early onset cataracts beset both non-sporting and sporting breeds more often.
So, while the studies show that mixed breeds aren’t immune to health conditions, they are generally less disease-prone than purebred dogs, who have a higher risk of health issues due to inbreeding. Whether or not a mixed breed dog comes out on top ultimately depends on the individual dog’s genetics and breed mixes, which influence their prevalence for disease.
Tracing health issues in dogs
So, how did all of these health glitches arise? Other research has found some diseases are more frequent in dogs of related ancestral origin. Younger breeds tended to have a higher likelihood of certain disorders, such as elbow dysplasia. Among the elbow dysplasia sufferers, four out of the top five breeds include the Bernese Mountain Dog, Newfoundland, Mastiff, and Rottweiler — all from mastiff lineage. The so-called “liability genes” may hail from founding ancestors of related breeds or be the result of human error in the quest for desired traits. And other diseases, such as hip dysplasia, seem to be more prevalent across all purebreds and mixed-breeds, indicating they are an ancient gene mutation.
References:
Health of Purebred vs Mixed Breed Dogs: The Actual Data
The Great Debate: Mutts Vs. Purebreds
Odds of Inherited Disorders Between Purebred Dog and Mixed Breeds
Prevalence of Inherited Disorders Among Mixed-Breed and Purebred Dogs
Ten Inherited Disorders in Purebred Dogs by Functional Breed Groupings
Lifespan of Companion Dogs Seen in Three Independent Primary Care Veterinary Clinics in the United States
Which Dog Lives the Longest? Smaller Dogs Have Longer Lives
Are Mixed-Breed Dogs Healthier Than Purebred Dogs?

Sheila Pell is a freelance journalist who frequently writes about environmental issues. Her work has appeared in The Washington Post, Modern Farmer, San Diego Reader, The Bark, and American Forests. She lives in northern California with her husband and two large dogs.

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