RALEIGH, N.C. — Dogs with dementia experience poor sleep, similar to humans, according to new research. Daytime napping is one of the earliest symptoms in Alzheimer’s patients, along with agitation or confusion around dusk and waking during the night. Now, scientists have discovered a comparable phenomenon in dogs.
“Our study is the first to evaluate the association between cognitive impairment and sleep using polysomnography – the same technique as used in sleep studies in people – in aged dogs,” says senior author Dr. Natasha Olby, a professor of veterinary neurology and neurosurgery at North Carolina State University.
The electroencephalogram (EEG), a test typically conducted to diagnose sleep apnea or heavy snoring, records brain waves, blood oxygen levels, heart rate, and breathing, as well as eye and leg movements. This test found the same reduction in sleep time and delta brain waves, which occur during REM (deep) sleep, in dogs with canine cognitive dysfunction syndrome (CCDS), the equivalent of dementia in dogs.
The findings suggest that dogs may hold the key to curing dementia, and testing on them first could fast-track clinical trials for humans.
The research team studied 28 male and female dogs between 10 and 16 years-old — the equivalent of being in their 70s and 80s in human years — across various breeds. Results show that dogs with higher dementia scores took longer to fall asleep and spent less time sleeping, both in NREM and REM sleep. Dogs with poorer memory scores exhibited other changes, such as fewer slow oscillations in their EEGs during REM sleep, indicating that they slept less deeply during this phase.
“In people, slow brain oscillations are characteristic of slow-wave sleep (SWS) and linked to the activity of the so-called ‘glymphatic system,’ a transport system that removes protein waste products from the cerebrospinal fluid,” Olby says in a media release. “The reduction in slow oscillations in people with Alzheimer’s, and the associated reduced removal of these toxins, has been implicated in their poorer memory consolidation during deep sleep.”
In contrast, dogs with poorer memory had more pronounced fast beta waves, between 15.75 and 19 Hz. Strong beta waves are typical of wakefulness in healthy people and dogs, and are not a normal phenomenon during sleep, further indicating that dogs with CCDS sleep less deeply.
Dogs that performed poorly on a “sustained gaze” task, which measures attention span, showed tighter coupling in delta waves between the two brain hemispheres – a result also found in people with dementia. The dogs with CCDS demonstrated changes in the sleep-wakefulness cycle during the experiments that resembled those found in people with Alzheimer’s.
Pet owners in the study had to complete a questionnaire about their canine companions, rating the severity of symptoms like disorientation, poor social interactions, and house soiling. The researchers also examined the animals for potential orthopedic, neurological, biochemical, and physiological conditions. Based on the results, eight dogs were classified as normal, while another eight, four, and eight dogs had mild, moderate, or severe CCDS, respectively.
The researchers then conducted a series of cognitive tests on the dogs to measure their attention, working memory, and executive control. In one example, a “detour task,” a dog had to retrieve a treat from a horizontal transparent cylinder by accessing it from either end, made more difficult by blocking their preferred side, requiring cognitive flexibility.
In a quiet room with dim light and white noise, the dogs were allowed to spontaneously take an afternoon nap while electrodes measured their brain waves, electrical activity of muscles and heart, and eye movements. These measurements lasted up to two hours but were stopped if the dogs became anxious, tried to leave the room, or removed the electrodes. It remains unknown if these changes also occur during dogs’ nighttime sleep, according to the researchers.
“Our next step will be to follow dogs over time during their adult and senior years to determine if there are any early markers in their sleep-wakefulness patterns, or in the electrical activity of their brain during sleep, that could predict the future development of cognitive dysfunction,” Olby says.
This research not only enhances our understanding of the sleep patterns and cognitive changes in dogs with dementia but also holds potential implications for human dementia research. By identifying early markers in dogs, it may become possible to develop more effective interventions or treatments for people suffering from Alzheimer’s and other forms of dementia.
The study is published in the journal Frontiers in Veterinary Science.
South West News Service writer Mark Waghorn contributed to this report.