Flat-faced dogs are most at risk of heat stroke, new study shows

A study has found that brachycephalic dogs with flat faces – such as bulldogs and pugs are more at risk of developing heat stroke.

Researchers in dog welfare at Nottingham Trent University and the Royal Veterinary College studied the clinical records of more than 900,000 dogs across the UK.

They found that more than 1,200 dogs had received veterinary care for heat stroke during the study, with almost 400 affected in a single year. This is just the tip of the iceberg as many dogs affected with heat stroke may not even be taken to a veterinary surgery.

Many of the breeds that were at increased risk were flat-faced meaning that they had a ‘brachycephalic’ skull with a shortened head, flat face and short nose.

The Labrador Retriever – traditionally the most popular UK breed – was used as the ‘base’ comparison breed to identify breeds at most risk.

The Bulldog, an extreme flat-faced breed, was 14 times more likely to develop heatstroke than Labrador retrievers, whilst flat-faced dogs in general were twice as likely.

Emily Hall, Lead Researcher and a veterinary surgeon at Nottingham Trent University’s School of Animal, Rural and Environmental Sciences said: “It’s likely that brachycephalic dogs overheat due to their intrinsically ineffective cooling mechanisms.

“Dogs pant to cool down – without a nose, panting is simply less effective. In fact, brachycephalic dogs may even generate more heat simply gasping to breath than they lose panting.”

The researchers state that the increasing popularity of these flat-faced breeds in concerning, particularly as climate change increases the severity and frequency of heat waves.

The Chow Chow and the Golden Retriever, which were also at high risk, have thick “double coats”, which limit effective cooling in hot weather, because the coat traps warm air against the body to prevent effective cooling from the skin.

The study published in the journal ‘Scientific Reports’, showed that heat stroke can have very severe effects in dogs, with one in seven dogs with heat stroke dying as a result of their illness.

Dr Anne Carter, Senior Lecturer in Animal Science at Nottingham Trent University, said: “Our research is particularly pertinent as the UK’s annual “Dogs die in hot cars” campaign has just been launched, a sad reminder that people still put their pets’ lives at risk every year by leaving them to suffer in hot cars. Our study also suggests that preventing obesity will reduce your dog’s risk of heatstroke.”

Dr Dan O’Neill, co-author and senior lecturer in companion animal epidemiology at The Royal Veterinary College, said: “As the UK moves progressively towards higher average temperatures due to global warming effects, we all need to wake up to the changing health hazards that our dogs will increasingly face.

“Greater understanding of which breeds, ages and types of dogs are at extra risk of heat-related illness can assist owners to select breeds that are more resistant to heat effects and to plan how best to protect predisposed dog types from their increased risk by, for example, altering times and levels of outdoor activity. Knowledge is power when it comes to protecting our beloved dogs. A core message from this study would be to “stop and think before buying a flat-faced dog.”

This study is part of the ongoing VetCompass research programme at the Royal Veterinary College that aims to improve companion animal welfare and was supported by a Dogs Trust Canine Welfare Grant.

Paula Boyden, Veterinary Director at Dogs Trust, said: “We are pleased to have been able to support this work. Dogs are unable to regulate their body temperature as well as humans do, so as the weather warms up, we need to be alert to the signs of heat stroke. These findings show that owners of flat-faced breeds and dogs who are overweight, need to keep an especially close eye on their beloved pet during the warm weather as they could be at greater risk.