Last Updated: 13/08/2026
Dog Dementia: Signs, Symptoms and Causes
Dog dementia affects 1 in 3 dogs by age 12. Our vet explains the signs, causes, and when to book a check-up for your senior dog.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 4 minutes - short read
Dog dementia is more common in senior dogs than most owners realise — and the signs are often dismissed as normal ageing. Technically known as Cognitive Dysfunction Syndrome (CDS), it's caused by physical changes to the brain that accumulate over time. If your golden oldie has started wandering aimlessly, 'forgetting' their house training, or staring into corners, they aren't just being 'difficult' - their brain may be undergoing real changes. This article covers the signs, causes, and when to get your vet involved.
For diet, supplements, enrichment, and medications, head to our companion guide: Dog Dementia Treatment: How to Help Your Senior Dog.
For a broad overview of caring for an older dog, our senior dog care guide is a great starting point.
In this article
What are the signs of dog dementia?
The most common signs of dog dementia (Cognitive Dysfunction Syndrome) are disorientation, changes in sleep patterns, house soiling, altered social behaviour, increased anxiety, and changes in activity levels - often appearing gradually from around 11 years of age.
These changes tend to creep in slowly, which makes them easy to write off as "just getting old." Here's what to look out for:
Disorientation Your dog may seem lost or confused in familiar surroundings - staring blankly at walls or into corners, getting stuck behind furniture, or waiting at the wrong side of the door to be let in.
Changes in social interaction Some dogs with CDS become withdrawn and lose interest in family members or other pets. Others go the opposite way and become unusually clingy. Either shift from their normal behaviour is worth noting.
Sleep-wake cycle changes Dogs with dementia often sleep more during the day and become restless or unsettled at night - sometimes pacing or vocalising when they'd normally be asleep.
House soiling A dog who has been reliably toilet trained for years may start having accidents indoors. This isn't stubbornness; they may have simply forgotten the routine, or lost awareness of the urge until it's too late.
Activity changes Some dogs become less active and less interested in things they used to enjoy, like walks or greeting people at the door. Others pace, circle, or wander aimlessly, particularly in the evenings.
Anxiety and vocalisation Increased restlessness, repetitive barking, and whining -especially at night - are common in dogs with CDS, and can be distressing for both the dog and their family.
If you're noticing any of these signs, book a vet check rather than assuming it's normal ageing. Many conditions that cause similar changes - including thyroid disease, high blood pressure, arthritis, and dental pain - are treatable, so it's important to rule those out first.
What causes dementia in dogs?
Cognitive dysfunction is caused by age-related changes to the brain, including:
- Oxidative damage
- Reduced brain mass
- Accumulation of beta-amyloid protein (a substance toxic to brain tissue)
- Reduced blood flow to the brain
- Dysfunctional neurons (nerve cells)
How common is dog dementia?
In dogs, it has been shown that 28% of dogs will show some signs consistent with cognitive dysfunction by 11-12 years of age, and 68% by 15-16 years of age.1
While any dog can develop dementia, a longitudinal study found that toy breeds, terriers, and nonsporting dogs were 3 times more likely to be diagnosed with CDS.2
When should I see a vet about dog dementia?
While it can be tempting to conclude that behavioural changes in our dogs are simply due to ageing, it is important to have your dog checked out by your veterinarian, to determine whether cognitive dysfunction may be contributing to the changes.
Cognitive dysfunction is a diagnosis of exclusion, which means that other possible medical causes of these changes should be ruled out first. These include:
- Hormonal diseases such as Cushings Disease and Hypothyroidism
- Arthritis
- Dental disease
- High blood pressure (often as a result of kidney disease)
- Cancer
- Diminishing sensory capacities (predominantly vision loss and hearing loss)
If your veterinarian does diagnose cognitive dysfunction in your dog, they may prescribe some specific medications to help reduce the decline. You can read more about these in our dog dementia treatment guide.
FAQs
References
Neilson JC, Hart BJ, Cliff KD, et al: Prevalence of behavioral changes associated with age-related cognitive impairment in dogs. J Am Vet Med Assoc 2001 Vol 218 (11) pp. 1787-91.
Yarborough S: Evaluation of Cognitive Function in the Dog Aging Project: Association with Baseline Canine Characteristics. Accessed 4/16/2025 University of Washington Press 2021.
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Thu 13 Aug 2026
Edited by Dr Gillian Hill BVSc (Hons)Dr Gillian Hill BVSc (Hons)
Veterinarian
Dr. Gillian graduated from the University of Sydney in 2005 with a Bachelor of Veterinary Science. She worked in a number of small animal clinics, before joining the Pet Circle Vet team in 2020. Dr. Gillian has special interests in ultrasonography, surgery and behaviour. Her favourite part of being a vet is being an advocate for the animals. She loves helping owners to make the best, evidence-based decisions for their pets, and seeing the beautiful bond that people have with their fur-babies.
