By Mark Waghorn via SWNS
Dogs with dementia sleep poorly, just like humans, according to new research.
Daytime napping is one of the earliest symptoms in Alzheimer's patients. Others include agitation or confusion around dusk - and waking during the night.
Now, scientists have discovered similar phenomena in man's best friend.
Senior author Professor Natasha Olby, of North Carolina State University, said: "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."
The skull cap, or electroencephalogram, test is usually carried out to diagnose sleep apnea, or heavy snoring. It records brain waves, blood oxygen levels, heart rate and breathing. It also measures eye and leg movements.
It found the same reduction in sleep time and delta brain waves, which occur during REM, or deep, sleep occurs in the dog equivalent of dementia, CCDS (canine cognitive dysfunction syndrome).
The findings add to evidence man's best friend may hold the key to curing dementia. Testing them on dogs first may enable clinical trials to be fast-tracked.
The U.S. team studied 28 females and males aged ten to 16 - equivalent to being on their 70s and 80s in human years. They were a variety of breeds.
Results showed that dogs with higher dementia scores took longer to fall asleep and spent less time sleeping. This was true for both NREM and REM sleep.
Dogs with poorer memory scores showed changes, such as fewer slow oscillations in their electroencephalograms, during REM sleep, indicating that they slept less deeply during this phase.
Olby said: "In people, slow brain oscillations are characteristic of slow wave sleep and linked to the activity of the so-called ‘glymphatic system, a transport system that removes protein waste products from the cerebrospinal fluid.
"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, so are not a normal phenomenon during sleep – again indicating that dogs with CCDS sleep less deeply.
Dogs which did worse at a ‘sustained gaze’ task, which measures attention span, showed tighter coupling in delta waves between the two brain hemispheres – a result that has also been found in people with dementia.
The dogs with CCDS showed changes in the sleep-wakefulness cycle during the experiments that resemble those found in people with Alzheimer's.
Owners had been asked to fill in a questionnaire about their canine companions, to rate the severity of symptoms like disorientation, poor social interactions, and house soiling.
The researchers also examined the animals for possible orthopedic, neurological, biochemical and physiological conditions.
Based on the results, eight were classified as normal while another eight, four, and eight had mild, moderate, or severe CCDS, respectively.
The researchers then performed a series of cognitive tests on the dogs, to measure their attention, working memory, and executive control.
For example, in 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 so they have to show cognitive flexibility.
In a quiet room with dim light and white noise, the dogs were then allowed to spontaneously take an afternoon nap, while electrodes measured their brain waves, the electrical activity of the muscles and heart, and eye movements.
These measurements lasted up to two hours, but were stopped if the dogs became anxious, attempted to leave the room, or removed the electrodes.
It is still unknown if these changes also occur during when dogs sleep at night instead of in the afternoon, said the researchers.
Added Olby: "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."
The number of dementia cases worldwide will triple to more than 150 million by 2050. The study is in Frontiers in Veterinary Science.