Head shape of flat-faced dogs impacts their sleep patterns

In recent years, the popularity of flat-faced dogs like french bulldogs has soared globally. However, this preference for certain physical traits in dogs has raised significant health concerns. 

Hungarian researchers have found a troubling correlation between the shape of a dog’s head and its sleep patterns and overall health.

The cost of breeding for appearance

Flat-faced, or brachycephalic, dog breeds are loved for their distinctive appearances, but these physical traits come with a high price. The shortened skulls of these dogs are linked to a range of health problems, including deteriorative changes in brain morphology, breathing difficulties, and sleep disturbances. 

In the U.S. and Hungary, the french bulldog has become the most common flat-faced breed, but its popularity contradicts the health issues these dogs face due to their physical structure.

The researchers noted that extremely flat-faced dogs, such as French and English bulldogs and pugs, live an average 3 to 4 years less than other dogs and often do not live to adulthood. Their shortened skull is associated with a distorted brain, but it is not yet known how this affects neural functioning.

Sleep problems in flat-faced dogs

The recent study investigated how the physical traits of flat-faced dogs affect their sleep. The researchers discovered that these dogs tend to sleep more, largely because they suffer from breed-specific sleep apnea, leading to increased daytime sleepiness. 

Their REM sleep phase is unusually longer than non-REM sleep, and their sleep EEG patterns show signs indicative of white matter loss, suggesting significant impacts on brain health.

Focus of the study 

The team examined the sleep patterns of 92 family dogs using EEG. “In the sleep lab, dogs spend about three hours with their owners. As nothing exciting happens, the dogs fall asleep quickly. Meanwhile, we conduct the electrical potential generated by the brain activity with electrodes glued to their scalps,” explained Anna Kis, a researcher at the HUN-REN Institute of Cognitive Neuroscience and Psychology.

“We wanted to investigate whether flat-faced dogs sleep differently from other dogs, as they are known to suffer from oxygen deprivation due to respiratory problems and therefore have poorer quality sleep,” explained Zsófia Bognár, a PhD student who has been researching brachycephalic dogs for many years.

“We found that the flat-faced dogs slept more in the three hours given to them during the study. More daytime sleep is probably compensation for insufficient sleep at night.”

Key insights

Ivaylo Iotchev, the first author of the study, suggests that flat-faced dogs may retain an infant-like sleep pattern, which could be a result of selective breeding for infant-like traits. 

“In the present study, we found that brachycephalic dogs had decreased beta waves and increased delta compared to dogs with longer noses. The frequency of sleep spindles increased. This pattern has previously been associated with poorer learning in dogs and loss of white matter in humans,” said Iotchev.

“There may be several reasons for our results. The most interesting of these is that it seems as if the flat-faced dogs have retained the sleep pattern of puppyhood, similarly to newborns who spend more time in REM sleep.”

Infant-like traits 

Enikő Kubinyi, a professor and head of the MTA-ELTE Lendület “Momentum” Companion Animal Research Group, noted that the selection for infant-like appearances may have inadvertently affected brain function in these breeds. 

“It is widely assumed that brachycephalic dogs are selected for infant-like traits,” said Kubinyi. “They have large heads and eyes, high foreheads and small noses because we humans find these traits irresistibly attractive. That’s how babies get us to care for them.” 

“It is possible that the selection of dogs to be infant-like in appearance has also infantilized their brain function.” 

“But this is a bold assumption for now. What is very likely, however, is that breeding for brachycephalic heads leads to potentially harmful changes in brain function.”

The research is published in the journal Brain Structure and Function.

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