Doggy dementia: Dogs’ risk of canine dementia rises by more than 50% each year, study finds

canine dementia
Maggie Davies

Large study could aid diagnosis in dogs and improve understanding of age-related illness in humans.

If you can’t teach your old dog new tricks, it could be an ominous sign. Researchers have found the odds of a canine having doggy dementia rises by more than 50% with each year of age.

While dementia is a well-known condition in humans, dogs can experience a similar decline in cognitive function, with symptoms including disrupted sleep, forgetfulness, walking into things, difficulties adapting to change and getting lost.

But while previous work has suggested such canine cognitive dysfunction (CCD) is more common in older dogs, as is the case in humans, studies have been small and prevalence is unclear.

Now a large study has shed fresh light on such matters in work researchers say could aid diagnosis of the condition in dogs – and even help humans.

“Given increasing evidence of the parallels between canine and human cognitive disease, accurate CCD diagnosis in dogs may provide researchers with more suitable animal models in which to study ageing in human populations,” the team wrote.

Writing in the journal Scientific Reports, researchers in the US reported how they analysed data from two surveys completed by the owners of 15,019 dogs, as part of the Dog Aging Project.

Owners were quizzed on aspects of their dogs’ behaviour including whether they had a tendency to get stuck behind objects or struggled to recognise familiar people, as well as factors such as the dog’s age, sex, breed, health and activity levels.

The team then assigned each dog a score between 16 and 80, with a score of 50 or higher indicating the dog had CCD.

The results, based on data collected between late 2019 and late 2020, reveal that 1.4% of the dogs had CCD.

After taking into account factors including whether the dog was sterilised, its breed, and other health problems, the team found the odds of CCD rose by 52% with each year a dog clocks up. However, the analysis suggests prevalence of the condition is almost zero in dogs below the age of 10.

The team also reported that the odds of CCD were 6.5 times higher among dogs with lower activity levels over the past year. While the researchers said exercise may be protective against cognitive decline, they cautioned their finding could also be down to dogs with CCD being less active because of their condition, while lockdowns and other Covid restrictions may have influenced the activity level of owners and their pets.

A history of eye, ear or neurological problems was also associated with greater odds of CCD, while it appeared terriers or toy breeds may be more likely to have the condition, although the team did not report whether this finding remained after factors such as age were considered.

The researchers added that estimating which quartile of life the dogs were in helped them tell apart those with and without CCD, suggesting the approach may help indicate dogs that should be screened for the condition.

Prof Clare Rusbridge, a veterinary neurologist at the University of Surrey, who was not involved in the study, said the research helps to address how common CCD is and added weight to evidence that lifestyle influences likelihood of dementia, but said owners can take preventive measures against CCD, including the use of special diets and engaging their dog in physical, intellectual, and social activities.

Gregor Majdič, professor of physiology at the veterinary school at University of Ljubljana, said the association between CCD risk and activity had not been seen before.

“One lesson that already stems from the current study is further proof that physical activity, also in older people, is very important for the wellbeing and for keeping ageing brain healthy,” he said.

Nick Sutton, dog health and science expert at the Kennel Club, agreed, but added the study highlighted a “sad irony” that while dogs are generally living longer thanks to our understanding of how to keep them healthy, the older they are, the more likely they are to suffer from age-related illness, including dementia.

“There is no cure for canine dementia or Alzheimer’s disease in humans, but by improving our understanding of these diseases, with research such as this, and by working towards a One Health approach, we can find better ways to prevent, identify, treat and eradicate these awful diseases,” he said.

Dogs with dementia also have sleep problems, finds study

Humans with condition can have disturbed sleep, and similar symptoms in dogs indicate cognitive decline is under way.

From loud snores to twitching paws, dogs often appear to have a penchant for a good snooze. But researchers have said elderly canines with dementia appear to spend less time slumbering than those with healthy brains – mirroring patterns seen in humans.

It has long been known that people with dementia can experience sleep problems, including finding it harder to get to sleep. Researchers have also found changes in the brainwaves of people with dementia during sleep – including decreased slow brain waves that occur during non-rapid eye movement deep sleep. These are important in memory consolidation and appear to be linked to the activity of the brain’s system for clearing away waste.

Now it seems sleep impairment may occur in dogs experiencing a condition similar to dementia in humans.

“Changes in sleep habits should be expected in older dogs, and could be a harbinger of decline in cognition,” said Prof Natasha Olby, senior author of a study at North Carolina State University. Writing in the journal Frontiers in Veterinary Science, Olby and colleagues reported on their study of 28 dogs aged between 10 and 16 years old. The canines’ brainwaves were recorded by electroencephalogram (EEG) while the dogs took a two-hour afternoon nap.

The researchers also assessed owners’ answers to a questionnaire and each dog’s performance on a range of problem-solving, memory and attention tasks, to provide a score indicating whether the dog had, or was at risk of, canine dementia. Twenty of the dogs were deemed to have cognitive impairment, with this judged to be severe in eight of them.

Combining their data, the team found dogs with higher dementia scores took longer to fall asleep and spent less time sleeping.

In addition the team found signs that dogs with a poorer performance on a memory task experienced shallower rapid eye movement sleep.

Nick Sutton, dog health and science expert at the Kennel Club, who was not involved in the work, welcomed the study.

“Humans with dementia often have disturbed sleep and this research suggests that we’re not alone,” he said. “Discovering that dogs with dementia may spend less time in certain essential stages of sleep is a fascinating finding, which demonstrates the importance of speaking to your vet if you notice any concerning changes in your dog, including unusual sleeping behaviours.”

While there is currently no cure for human or canine dementia, Olby said the team hope to follow dogs before and during progression of dementia to identify changes early on that might serve as predictors of future problems.

“Understanding then allows us to look for ways to treat the underlying disease,” said Olby, adding successful treatments in dogs could help pave the way for treatments in humans.“ Thus it is a win win for dogs and their owners,” she said.

(Article source: The Guardian)

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