If you've got an older dog that's acting a little unusual, and you think it's just old age — think again.

Getting stuck behind furniture, not sleeping at night or becoming increasingly anxious can all be signs of dementia.

By the time your pooch reaches the age of 14, she or he has a 40 per cent chance of developing canine cognitive dysfunction (CCD).

Scientists began to recognise the condition in dogs some two decades ago, and have amassed a large body of research into it. But many pet parents are surprised when it happens to their dog.

Its prevalence comes down to the extended lifespan of our much-loved pets, said Tom Duncan, a researcher with the University of Sydney's Brain and Mind Centre.

"We are prolonging the lives of dogs far beyond what a wild dog would be expected to live to, " Dr Duncan said.

"We have great veterinary care now and so we're able to treat conditions that may have before affected the dog's life span.

"This older dog population is ageing just like in humans, and so we see an increased prevalence of this disease."

Veterinarian Cameron Fay sees cases of dementia in dogs at least once a week at his clinic in Sydney's Inner West.

Dr Cameron Fay said dementia in dogs can happen quickly ( Nadyat El Gawley )

He says while people are aware of dementia in humans, the problem with identifying it in animals is that it can happen quickly.

"With dogs and cats, everything is in fast forward. You've got a puppy, then an adult dog … a senior, and finally the geriatric. And that happens in a short space of time. Sometimes it's a matter of months [where] you can see that mental decline in them, " Dr Fay said.

The disease is 'shattering'

Cynthia Forshaw is a passionate advocate for dogs.

Since she retired 15 years ago, she has been a volunteer at Doggie Rescue, a Sydney-based animal shelter.

Ms Forshaw recently lost Molly, her 18-year-old bichon poodle-terrier cross, to dementia.

Molly began to show signs of dementia not long after she turned 16. There wasn't an official diagnosis, but Ms Forshaw noticed Molly's behaviour began to change.

She would get stuck behind open doors and sofas and would "scream" because she couldn't get out.

"There was one occasion where she actually forced herself through the front gate," Ms Forshaw recalled.

"[She put her head] through the front gate, and didn't know how to go backwards so she literally forced her whole body through the front gate.

"I heard this screaming and was running around looking for her. She'd gone into next door and got her head stuck in some wire fencing in their front garden."

Ms Forshaw was shattered by the changes in Molly.

Molly began to show signs of dementia after she turned 16. ( Cynthia Forshaw )

Research could also help humans

Veterinarian Kaylene Jones has witnessed the impact dementia can have both on the dog and its owner.

"Because of the profound effect of the disease on the dog's life and the bond between the pet and their owner, there's a very real urgency for the discovery of new treatments," Dr Jones said.

She is currently working with Dr Duncan at the Brain and Mind Centre looking at the possibility of treating dementia in dogs with stem cells.

What to look out for? Symptoms of dog dementia can include: Sleep disturbances

Sleep disturbances Generalised anxiety

Generalised anxiety Inappropriate vocalisation (howling, barking or whining)

Inappropriate vocalisation (howling, barking or whining) Repetitive behaviour, such as pacing

Repetitive behaviour, such as pacing Staring at walls

Staring at walls Fewer social interactions

Fewer social interactions Disorientation and getting lost

In 2015, they treated Timmy, a 14-year-old cocker spaniel, using stem cells derived from the dog's skin.

His behaviour settled down following the treatment, according to anecdotal reports from his owners.

The researchers were able to achieve similar results in a second dog, Leo.

While the trial is still in its early stages, the researchers said the preliminary results from the two cases were "promising".

And there could be benefits from exploring this line of research in humans.

"We think if it works in dogs, it stands a very high chance of working in humans just because of the close similarity between the dog and the human brain," Dr Duncan said.

"We are using canine dementia as a model for humans."

Life turned upside down

Alex Williams' life radically changed when her old rescue dog Murphy was diagnosed with dementia.

The 29-year-old, who lives in Arizona, was devastated by Murphy's dementia and felt the impact emotionally and physically. Both she and her partner were constantly sick, and hardly got any sleep.

"We were running on two hours of sleep within 24 hours. It was constant attention to Murphy," she said.

"In your mind as their mum, you'd be thinking: 'Do we put him to sleep, do we keep him alive? Are we keeping him alive for us? Is he living a good quality life?'

"It was a very traumatising disease."

Alex and partner Glenn with their dogs - from left to right - Max, Ella, Murphy, Chingy and Pita ( Supplied )

Ms Williams has been rescuing dogs for 10 years. She found two of her four dogs — Max and Ella — on the side of the road while driving to Arizona's capital city Phoenix.

Ms Williams was not aware that dogs could get dementia and it was difficult for her to watch the effect of the disease on Murphy.

"You know, a dog gets cancer or has diabetes, you can see they're physically sick. I think it's a lot easier," she said.

"[Murphy] would kiss us and he would be excited to eat.

"His body wasn't sick, his mind was sick. That was a really hard thing for me to understand.

"It was like he's still okay, but it's really not okay."

Murphy's dementia would keep him awake at night when his anxiety and confusion would increase. He paced constantly.

"When he would pace, he would fall over, and then he'd walk into corners or into the back side of the door," recalled Ms Williams.

"He struggled to get up, so you'd help him up [and] he'd go walk, then come back in, lay down and then get back right up.

"It was exhausting for him towards the end. And he would end up dragging his back legs. It wasn't good."

Letting go

Ms Forshaw didn't sleep the night before she took Molly to the vet.

"Something had snapped."

Molly paced in circles all through the night, and Ms Forshaw couldn't console her.

"She no longer recognised me … and if I tried to calm her, she would just scream at the top of her lungs. That's why I'd say it's not for me to make the decision. Dogs let you know when it's time.

"My pact with my fur-kids is that I will be the last voice they hear, the last eyes they see and the last touch they feel at the end of their life. For the love and joy they give you, you can't do it any other way."

"He lost the sparkle in his eye" said Murphy's owner Alex. ( Supplied )

The day Ms Williams and her partner Glenn farewelled Murphy is a day she won't forget.

Murphy was pacing and falling over and when they took him outside to urinate, the wind blew him over.

"And that's when it was … 'OK, we're keeping him alive for us.' You could just tell he'd lost the sparkle in his eye," Ms Williams said.

"He went really easy. He gave my boyfriend a kiss on the nose [and] he just went.

"It wasn't like he fought it. He didn't twitch, he didn't cry, he didn't do anything. And the vet said that when dogs go that fast, it means their bodies are done fighting."

'Keep them energised and stimulated'

There is currently no cure for dementia in dogs, but Dr Fay recommends keeping your dog as engaged as possible.

"Keep them stimulated, get them outside … play games and stay interactive with them, " he said.

Much like Alzheimer's disease in humans, treatment of doggie dementia is all about alleviating the symptoms such as pacing and anxiety.

"My experience with medications is that they're not miracle cures," Dr Fay said.

"But as I always say to people it's important that [the dog] stays as active as possible.