Dementia in dogs

Overview

Age-related brain changes

Dementia is a progressive, age-related brain disease. Its impact appears in how dogs manage previously learned daily tasks. A familiar cue, such as a learned word, may no longer prompt the usual response.

Cerebral cortex atrophy is one associated change. Dogs may initially seem merely absent-minded because mild changes appear only occasionally.

Normal function may remain during mild disease despite small changes in familiar behaviour. As disease progresses, occasional changes can become repeated disruptions to daily routines.

A research project from northern Europe is investigating brain tissue changes associated with canine cognitive decline during 2024–2027.

Different studies have classified 14–35% of dogs over eight as cognitively impaired. Estimates depend on the behaviours measured and questionnaire cut-off.

Causes

Nervous tissue changes

Gradual degeneration changes how dogs process information. Beta-amyloid can accumulate in the brain as protein deposits called plaques. The cerebral cortex can thin. Some affected dogs also have enlarged brain ventricles.

Concurrent conditions, such as joint pain or impaired vision, can worsen individual symptoms.

Amyloid can also accumulate around cerebral blood vessels. Ageing brain cells can lose protection against oxidative injury. Increased activity of a neurotransmitter-degrading enzyme can reduce brain dopamine.

Neurons can be lost from the hippocampus, involved in memory and navigation. Amyloid and oxidative injury can activate brain support cells into prolonged inflammation. Myelin protecting nerve fibres can be damaged in white matter.

Risk factors

Age is a key associated factor. In a US survey covering pet dogs of all ages, 1.4% exceeded the cognitive dysfunction cut-off used. Each additional year had an odds ratio of 1.52 after accounting for other measured differences.

Dogs owners rated inactive had an odds ratio of 6.47 compared with very active dogs. Inactivity can also result from developing cognitive dysfunction. Previous eye or ear disease was associated with greater likelihood in the same population.

Although signs become more common with age, onset varies by size. Large dogs may show initial signs at six to seven years. Small dogs more often first show signs at eight to 10.

The owner survey also associated previous neurological disease with greater likelihood of dysfunction. Findings on associations with sex and remaining entire have been inconsistent.

Typical symptoms

Assessment covers navigation, interaction, sleep, house-training, activity and anxiety.

• Standing at the wrong side of a door or becoming stuck in corners.
• Wandering aimlessly indoors.
• Avoiding stroking or seeking more human company.
• Sleeping more by day and staying awake at night.
• Urinating or defaecating indoors despite previous house-training.
• Losing interest in familiar games.
• Becoming anxious in situations previously handled calmly.

Learning new tasks can slow. Finding food dropped on the floor may become harder.

Some dogs develop new noise sensitivity, for example to loud sounds or thunder. Separation anxiety can also begin later in life, causing clear distress when left alone.

Dogs may greet familiar people less often as their social behaviour changes. They may sometimes stare at walls or into space.

Complications and consequences

Effects on daily life

Progressing behavioural changes can increasingly restrict function. Night-time restlessness may involve repeated wandering or vocalisation. Separation-related anxiety can impair quality of life.

In 24-month follow-up of dogs over eight, four mildly affected dogs, or 22%, progressed to dementia. In the same 51-dog follow-up, dementia diagnosis was not associated with shorter survival.

Of initially unaffected dogs, 33% moved into the mild impairment group over those 24 months. Progression rate varies considerably between dogs.

Night-time wandering or vocalisation can also disturb owners' sleep.

Diagnosis at the vet

Investigating behavioural changes

The vet establishes when behaviour changed and whether observations are new. Questionnaires can assess getting lost, house-training and sleep–wake changes. They consider frequency and change over time. Repeating the same questionnaire helps track progression.

Investigating other illnesses

General examination looks for pain and diseases that alter behaviour. Impaired vision or hearing can explain some changes. Blood counts and biochemistry can identify systemic illnesses causing similar signs. Behaviour is reassessed after treating another potentially explanatory disease.

Focal neurological deficits can suggest a brain tumour or vascular disorder, for example. MRI can look for other structural causes when needed. Extended assessment can include cerebrospinal fluid examination alongside MRI.

Urinalysis is a basic investigation for other causes of house-soiling or behavioural changes. Joint pain can cause indoor urination if stairs make outdoor access difficult, for example. Cushing's disease can increase urination and cause accidents.

Questionnaire scores and follow-up

Owners can complete questionnaires such as CCDR and CADES from their observations. CADES covers navigation, interaction, sleep–wake rhythm and house-training. CCDR scores of 40–49 can suggest mild impairment or increased risk. Questionnaires may grade the same dog differently, so scores are interpreted with other findings.

A CCDR score of at least 50 exceeds its cognitive dysfunction screening cut-off. CADES scores of eight to 23 fall within mild impairment. In a comparison, CADES classified five dogs as severely affected. CCDR classified seven as at risk. None exceeded the CCDR dementia threshold. Questionnaires can screen at the clinic, but no single test confirms dementia in a living dog.

Treatment

Medication and symptom management

Treatment aims to relieve signs and support daily life. The vet may consider selegiline, which affects brain dopamine. Separate symptom-relieving medication may address night-time restlessness or anxiety. Predictable routines can reduce confusion and stress.

Selegiline inhibits an enzyme breaking down dopamine and other neurotransmitters. Possible adverse effects include vomiting, diarrhoea or reduced appetite. An open-label follow-up of 641 dogs found improvement in 77.2% at 60 days after treatment began.

Changes observed in diet trials

A dietary comparison involved 24 veterinary practices in Ontario. Participating pet dogs were nine to 16 years old. They were randomly assigned to three diet groups, initially with 29 dogs each. Signs were assessed at 30 and 90 days. All six behavioural domains improved by 90 days in the group receiving 6.5% medium-chain triglycerides and other supplemented nutrients. Control food dogs improved in four of six domains. Assessment used owner-completed symptom questionnaires.

Of 26 dogs completing the 6.5% medium-chain triglyceride diet, 23 improved or remained stable. Improvement in five of six domains was present by day 30 in that group. Alongside fatty acids, the test food included vitamins E, C and B-group vitamins.

Prevention

There is no certain way to prevent cognitive decline. Regular exercise adapted to ability helps maintain activity with age. Suitable feeding enrichment and short training sessions offer opportunities to use learned skills. More active dogs had less owner-reported decline over the preceding six months.

Other illnesses also reduce activity, so this association does not establish how much exercise affects disease development.

Older dogs' health checks can identify mild behavioural changes before substantial daily impairment.

Important for dog owners

Maintain familiar feeding, walking and bedtime routines to make events predictable. Keep furniture in familiar positions if navigation is difficult. A night light can help movement in darkness. Make water, food and bedding easy to find. Add brief toilet trips if accidents increase. Record what changed, when and how often for the appointment.

With hearing loss, supplement familiar commands with hand signals if vision allows. Use favourite rewards when relearning commands or house-training routines.

Report new mobility difficulties because joint pain can affect sleep and behaviour.

Frequently asked questions

How can I distinguish dementia from normal ageing?

Look for new, repeated changes impairing daily function. Getting lost at home or losing house-training can reflect cognitive decline. The vet also investigates pain, sensory changes and other diseases.

Can canine dementia be treated?

Treatment supports daily life and relieves signs of this gradually progressive disease. Medication may be assessed for anxiety or night-time restlessness. Familiar routines and routes through the home can reduce confusion.

Why does my dog wander or vocalise at night?

Dementia can alter sleep–wake rhythms, increasing daytime sleep and night waking. Restlessness can also have other causes such as pain. Record its timing and what your dog does.

Is MRI needed?

Assessment starts with history and clinical examination. Brain MRI can investigate a tumour or other focal lesion. Extended assessment may add cerebrospinal fluid examination.

Why is a house-trained dog having accidents?

Dogs with dementia can forget to ask to go out or lose learned toileting habits. Investigate the cause because other diseases can also affect house-training. More frequent toilet trips can reduce accidents meanwhile.