Flat-faced dog breeds are popular all over the world. In the USA and in Hungary, the French Bulldog is currently the most common breed. However, their popularity comes at a high cost in terms of health: shortened skulls are associated with deteriorative brain morphology changes, breathing difficulties and sleep problems. According to recent findings by Hungarian researchers, flat-faced dogs sleep more because their breed-specific sleep apnea increases daytime sleepiness, their REM sleep phase is longer than non-REM sleep, and their sleep EEG patterns show signs of white matter loss. 

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Source: https://biologia.elte.hu/