Study finds connection between skull shape and different sleep patterns in canines that could have further health implications.
The domestic dog’s evolutionary journey has been shaped not only by companionship but also by selective breeding. One of the most visually striking changes induced by selective breeding is the transformation of the cranium, measured using a metric called the cephalic index (CI). A Hungarian study explores the correlation between cephalic index values and sleep patterns, highlighting the links between anatomy, physiology, and behavior in dogs.
Cephalic Index and Brachycephaly
The cephalic index (CI) serves as a numerical expression of the skull’s shape, specifically the ratio of skull width to skull length. When this ratio exceeds 60, it denotes brachycephaly a trait characterized by a short muzzle and a flat face. Many popular dog breeds, such as Bulldogs, Pugs, and Boxers, showcase brachycephalic features, which have been selectively bred over generations.
Sleep Physiology and White-Matter Loss
The study explores sleep physiology to measure the impact of cephalic index values on canine brain dynamics. Using non-invasive sleep electroencephalography (EEG), researchers identified markers of white-matter loss during sleep. Dogs with higher cephalic index values displayed specific sleep-physiological patterns, including high delta power and low frontal spindle frequency. These markers, associated with white-matter loss, hinted at potential neuroanatomical changes linked to brachycephaly.
Sleep Duration and REM Patterns
Brachycephalic subjects exhibited longer sleep durations, suggesting a potential connection to the sleep apnea commonly observed in these breeds, which can contribute to increased daytime sleepiness. Furthermore, the study exposed patterns within the Rapid Eye Movement (REM) sleep stage. Brachycephalic dogs spent more time in REM sleep compared to non-REM, and REM duration correlated positively with the number of REM episodes across dogs. These findings prompt questions about the origins of these sleep patterns whether they stem from breathing difficulties, or are influenced by neuro-psychological conditions associated with brachycephaly.
The study highlights the potential impact of brachycephaly on neural systems, as evidenced by sleep EEG markers. The connection between skull shape and sleep patterns opens a window into understanding the canine brain’s dynamics, offering valuable insights for veterinary professionals and researchers.
