Alzheimer’s disease and Canine Cognitive Dysfunction
Like humans, many dogs will experience some degree of decline in memory and cognitive function as they get older. Is this a normal part of aging in dogs? Not necessarily.
A decline in brain function is more likely due to Canine Cognitive Dysfunction (CCD), which is very common in older dogs. This disease is the equivalent of Alzheimer’s Disease in humans. Approximately, 14-35% of elderly dogs over 8 years of age will experience CCD, with the chance of getting it increasing the older a dog gets. The subtle signs of early disease are often overlooked and dismissed as a normal part of aging, but the symptoms often progress to more severe cognitive impairment. Most importantly, patients with CCD typically respond quite well to medical interventions, especially if instituted early. Early recognition and intervention can significantly improve quality of life in elderly dogs.
Symptoms of canine cognitive dysfunction
In humans, Alzheimer’s Disease is characterised by an initial decline in memory followed by a progressive decline in other cognitive functions. CCD is similar. It is slowly progressive, over months to years, and symptoms may include:
- Disorientation and confusion (such as trouble recognizing people, difficulty locating food, getting lost or stuck in familiar environments, failure to recognise familiar people, trouble navigating stairs and tight spaces)
- Decreased interactions with people and other pets
- Altered sleep-wake cycles – night-time wakefulness
- Aimless wandering or compulsive circling
- Pooing or weeing in the house (reversion of toilet training)
- A decreased awareness of the surroundings and external stimuli
- Apparent hearing loss
- Increased agitation and anxiety
- Excessive vocalisation
- Episodes of vestibular disease (balance issues and eye twitches)
- Intermittent seizures
The gradual decline in cognitive function in both CCD and Alzheimer’s Disease correlates with physical changes in the brain. There is brain vascular disease and the accumulation of β-amyloid protein in the brain, which is toxic to brain cells. This protein accumulates as plaques around nerve cells and blood vessels, especially in the cerebral cortex and hippocampus (the thinking and memory parts of brain). The amount of β-amyloid accumulation correlates with the degree of cognitive impairment. Other changes in the brain include reduced brain volume, nerve cell loss, tiny haemorrhages, blood clots, and alterations in the brain chemical pathways. There are multiple and complex deleterious changes that all contribute to altered impaired brain function.
Alzheimer’s disease, in humans, may progress from a pre-clinical stage to mild cognitive impairment, to fully diagnosed disease. A pre-clinical stage may also occur in dogs, beginning with impaired spatial memory.
Early treatment in humans has been shown to delay the progression of cognitive decline. Early treatment of CCD has the same benefits as well.
Interventions
The primary strategy with helping dogs with CDS is the reduction of risk factors that contribute to brain aging and decline. Slow the decline by therapies that aim to reduce brain inflammation and damage, slow the destruction of brain cells, and restore lost nutrients and brain chemicals. Best results are obtained by combining mental stimulation with antioxidants and nutraceuticals, as well as medications.
Mental Stimulation – use it or lose it
Mental stimulation enhances cognitive function and decelerates the degradation of brain cells – the ‘use it or lose it’ principle. For dogs, facilitate mental stimulation through training activities, play, exercise, and interactive toys (e.g., food-dispensing toys that necessitate manipulation). Diversify exploration opportunities by concealing treats in various locations. Also, dogs with CCD often have an altered day-night cycle. Open blinds and provide mental engagement and activity during the day to try to mitigate nighttime wakefulness.
Nutritional supplements – antioxidants and anti-inflammatories
- Antioxidants: Free radicals are waste products in the body that damage DNA and proteins, disrupting cell function and causing cell death. Increased free radical damage is found in the brains of CCD patients. Antioxidants, like vitamins E and C, selenium, and flavonoids can destroy free radicals. A study showed improved cognition and fewer plaques in the brains of dogs on a high antioxidant diet after 2-8 weeks.
- Medium chain triglycerides: Aged brains may be better able to get energy from medium-chain triglycerides, rather than sugar. In humans with AD, medium-chain triglycerides can enhance cognitive performance and are approved as a supplement for AD. The same may be true for dogs with CCD.
- Omega-3 fatty acids: Omega-3 fatty acids, found in fish oil, are important for brain function and have anti-inflammatory properties. Supplementation of omega-3 fatty acids in the diet has been shown to enhance cognitive function.
- Other dietary supplements that have shown improvements in symptoms associated with CCD include phosphatidylserine, S-adenosyl-L-methionine (SAMe), and apoaequorin. Curcumin, found in turmeric, possesses antioxidant and anti-inflammatory properties, and may reduce amyloid-beta protein involved in plaques. Ginko Biloba may also be helpful.
There are prescription diets specific for brain aging and CCD, along with veterinary dietary supplements containing varying mixes of the above ingredients. Two commercial diets with evidence of efficacy are Hills b/d and Purina One Vibrant Maturity 7+.
Medications:
Medications can play a role in treating CCD. Dogs with CCD often have lower levels of brain chemicals known as neurotransmitters. L-denepryl (in Selegiline) may help restore dopamine and other neurotransmitter levels in the brain and has been shown to improve brain function in dogs with CCD. It may also protect the brain from free radical damage.
Propentofylline may enhance blood flow to the brain, heart, and muscles, and is approved for treating dullness, lethargy, and depressed demeanour in older dogs.
More recently, levetiracetam, traditionally an anticonvulsant drug, has shown to improve cognitive dysfunction and reduce hyper-excitability.
Anti-anxiety medications can help dogs with anxiety. Melatonin and sedatives are used for nighttime wakefulness. Calming pheromones, such as dog appeasing pheromone, can also be effective. Pain from conditions like arthritis influences sleep quality and mood in older animals. Therefore, medications and strategies to manage pain are important.
Early recognition and interventions can significantly affect quality of life
Early intervention is essential for effectively slowing the progression of canine cognitive disease. Most medications and supplements for CCD require several weeks before clinical improvement is evident. If your older dog exhibits signs of diminished brain function, it is advisable to consult a veterinarian and promptly implement strategies to slow brain aging.