Dogs brain-wave readings during sleep linked with indicators of cognitive deterioration
Washington, US: Dogs with dementia experience the same sleep interruptions as people with dementia. North Carolina State University researchers used electroencephalography, or EEGs, on senior dogs to see if brain-wave readings during sleep linked with indicators of cognitive deterioration. They discovered that dogs with advanced dementia had more sleep interruptions and slept less than dogs with normal cognitive functions.
The study, which was conducted as part of an ongoing clinical trial on canine ageing and cognition at NC State, included 28 elderly dogs: 17 females and 11 males. The dogs got thorough physicals, cognitive tests, and their owners completed the Canine Dementia Scale (CADES) questionnaire prior to the sleep study to establish the severity of their cognitive deterioration.
The electrodes were fastened to the pups' skulls with sticky gel, and the dogs were not anaesthetized while the researchers collected data. The dogs slept in the lab twice: once to acclimatise them to the environment and electrode implantation, and once to capture brain activity during a two-hour sleep period.
"Past sleep studies in dogs often involved surgically implanted electrodes," says Alejandra Mondino, postdoctoral researcher at NC State and lead author of the study. "Non-invasive studies are relatively new. We are one of a handful of groups doing this work."
The EEG measured four stages of sleep: wakefulness, drowsiness, NREM and REM. NREM, or non-REM, is a deep sleep state prior to REM (which stands for rapid eye movement and is associated with dreaming).
"In NREM, the brain clears toxins, including the beta-amyloid proteins that are involved in diseases like Alzheimer's," Mondino says. "REM sleep is when dreams happen, and this stage is very important for memory consolidation."
The researchers correlated the percentage of time spent in each sleep state with the dogs' scores on cognitive testing and the CADES questionnaire. The higher the dog's dementia score, the less time they spent in NREM and REM sleep.
"These dogs have dementia and sleep disruption is part of that," Mondino says. "In addition to the shorter time spent sleeping, when we look at the EEG, we saw their brain activity during sleep was more akin to wakefulness.
"In other words, when they do manage to sleep, their brains aren't really sleeping."
The work is an important part of establishing baselines for identifying cognitive decline in dogs. The researchers hope that the work can lead to early diagnosis and intervention for elderly dogs with signs of cognitive decline.
"We now know that EEG signatures are useful indicators of canine cognitive dysfunction," says Natasha Olby, the Dr. Kady M. Gjessing and Rahna M. Davidson Distinguished Chair in Gerontology at NC State and corresponding author of the study. "The work further establishes the dog as a model for Alzheimer's disease. Hopefully therapeutic trials in dogs will help to direct our choices of treatment development for people."
