Sleep and cognition in aging dogs. A polysomnographic study

Abstract

IntroductionSleep is fundamental for cognitive homeostasis, especially in senior populations since clearance of amyloid beta (key in the pathophysiology of Alzheimer's disease) occurs during sleep. Some electroencephalographic characteristics of sleep and wakefulness have been considered a hallmark of dementia. Owners of dogs with canine cognitive dysfunction syndrome (a canine analog to Alzheimer's disease) report that their dogs suffer from difficulty sleeping. The aim of this study was to quantify age-related changes in the sleep-wakefulness cycle macrostructure and electroencephalographic features in senior dogs and to correlate them with their cognitive performance.MethodsWe performed polysomnographic recordings in 28 senior dogs during a 2 h afternoon nap. Percentage of time spent in wakefulness, drowsiness, NREM, and REM sleep, as well as latency to the three sleep states were calculated. Spectral power, coherence, and Lempel Ziv Complexity of the brain oscillations were estimated. Finally, cognitive performance was evaluated by means of the Canine Dementia Scale Questionnaire and a battery of cognitive tests. Correlations between age, cognitive performance and sleep-wakefulness cycle macrostructure and electroencephalographic features were calculated.ResultsDogs with higher dementia scores and with worse performance in a problem-solving task spent less time in NREM and REM sleep. Additionally, quantitative electroencephalographic analyses showed differences in dogs associated with age or cognitive performance, some of them reflecting shallower sleep in more affected dogs.DiscussionPolysomnographic recordings in dogs can detect sleep-wakefulness cycle changes associated with dementia. Further studies should evaluate polysomnography's potential clinical use to monitor the progression of canine cognitive dysfunction syndrome.

Tools and techniques for classifying behaviours in canine epilepsy

“…Similar to people with Alzheimer's disease, caregivers of dogs with CCDS often report that their dogs have difficulty sleeping. Using polysomnographic recordings and cognitive testing, CCDS dogs with higher dementia scores were found to spend less time in REM and NREM sleep during a two-hour window than dogs with lower dementia scores (37). This further highlights the efficacy of EEG for investigating sleep patterns in dogs with neurological diseases.…”

“…Clinicians and researchers use EEG to correlate the cortical activity of REM sleep with behaviours such as chewing, biting, or barking to confirm REM sleep behaviour disorder diagnoses thus distinguishing these behaviours from sleepassociated seizures. Polysomnography has also provided insight into the relationship between sleep quality and cognition in dogs with canine cognitive dysfunction syndrome (CCDS) (37). Similar to people with Alzheimer's disease, caregivers of dogs with CCDS often report that their dogs have difficulty sleeping.…”

Beacon-based sleep-wake monitoring in dogs

“…Dog sleep research is attracting attention in the veterinary field, and reductions in sleep and activity due to temperament [ 12 ] and diseases such as pain and motor dysfunction [ 9 ] were reported. Also, as dogs’ behavior and neurological function have been focused on as models for human ageing, cognitive dysfunction, and neurological disorders [ 3 , 10 , 13 ], long-term automated monitoring of dog’s sleep and movement is also expected to contribute to translational research in dogs.…”

“…Various factors, such as exercise, environments and aging influence the sleep patterns of dogs [ 4 , 7 , 10 ]. Moreover, there is evidence suggesting that sleep is associated with memory formation in dogs [ 13 ]. These findings support resemblance to those observed in the human.…”

Development and validation of a sleep questionnaire, SNoRE 3.0, to evaluate sleep in companion dogs

“…We have recently demonstrated in senior dogs a negative correlation between their sleep time and their cognitive function 51 . Therefore, senior dogs with cognitive impairment were expected to have higher mSNoRE values.…”