Explaining canine cognitive dysfunction to pet owners can be challenging. The condition cannot be definitively diagnosed and there is very little scientific evidence to explain its existence, yet we know that it occurs in our aging canine patients.
In this article we provide an overview of the syndrome’s symptoms and treatment options.
What is canine cognitive dysfunction?
Canine cognitive dysfunction is defined as “age-related cognitive decline that cannot be attributed to other medical conditions, such as sensory deficit, infection, or cancer.”
Cognitive dysfunction in dogs is analogous to Alzheimer’s disease in humans; in fact, canine cognitive dysfunction has been used as a model for the study of Alzheimer’s.
The two conditions not only share similar clinical signs, but also share similar histopathological changes. Canine cognitive dysfunction patients demonstrate cerebral amyloid angiopathy and amyloid plaques in the brain, both of which are characteristic findings in Alzheimer’s disease.
Clinical signs checklist
Much of the challenge in diagnosing canine cognitive dysfunction relates to the considerable variation that can be seen in the course of the disease. Some dogs experience significant cognitive changes with aging, while others show only mild cognitive deficits.
The clinical signs of canine cognitive dysfunction can be summarized with the acronym DISHA:
- Sleep changes
- Activity changes
The following checklist can be used to question clients regarding signs of canine cognitive dysfunction in their pet.
- Have you noticed your dog dropping food, then seeming to “lose” the food or not pick it up?
- Is your dog wandering off to odd locations in your home?
- Does your dog seem to get lost more easily within your home or backyard?
- Is your dog more clingy than usual?
- Is your dog more distant than usual?
- Is your dog more irritable than usual?
- Is your dog waking more frequently than usual at night?
- Is your dog sleeping more than usual during the day?
- Has your housetrained dog started having accidents in the home?
- Has your pet become more restless than usual?
- Is your pet more lethargic or sluggish than usual?
- Is your pet showing more anxiety than usual?
Traditionally, canine cognitive dysfunction has been regarded as a concern in dogs starting at approximately 11 years of age. Based on more recent studies, however, it is now known that cognitive decline in dogs can begin as early as 6 to 8 years of age. While this early decline may not be obvious in most pets, it can be seen in highly-trained dogs such as service dogs and working dogs, since their daily function requires a greater level of mental acuity.
A Canine Cognitive Dysfunction Rating Scale (CCDR) has been developed by the University of Sydney to objectively assess canine patients. This rating scale covers the factors mentioned above, asking owners to comment on the frequency with which they observe these behaviors. It can be a valuable tool in assessing patients with suspected cognitive dysfunction.
Treating dogs with Alzheimer’s
The first step in treating canine cognitive dysfunction is to rule out medical conditions that may cause similar signs.
Neurologic conditions, endocrinopathies, chronic pain, dental disease, and many other conditions can cause signs that may be difficult to distinguish from cognitive dysfunction. Therefore, a thorough physical exam, complete blood cell count, serum biochemistry, and urinalysis are recommended before considering treatment for suspected cognitive dysfunction.
Next, it’s important to have a conversation with the dog’s owner in order to set realistic expectations. While the decline associated with canine cognitive dysfunction can potentially be slowed, it is unrealistic to expect these pets to return to completely normal functioning. Some degree of environmental management will likely always be required, even with effective treatment.
Dogs with cognitive decline often benefit significantly from environmental enrichment and training delivered by their owners. Mental stimulation can help slow age-related decline in cognitive function, similar to the “use it or lose it” mentality often employed in human aging. Owners can try introducing new toys, exercising their dog regularly, and sticking with a predictable daily routine.
Selegiline (also known as L-deprenyl) is a selective and irreversible inhibitor of monoamine oxidase B in dogs. This enzyme is increased in dogs with cognitive dysfunction and it is thought to play a role in free radical damage within the central nervous system; therefore, selegiline is thought to decrease free radical damage.
Selegiline also enhances the function of dopamine and other catecholamines in the cortex and hippocampus. It does this by increasing the activity of the neuromodulator 2-phenylethylamine (2-PEA) in the brain.
The recommended dose of selegiline is 0.5-1.0 mg/kg/day. Selegiline is sold under the brand name Anipryl®.
Nutritional therapy and dietary supplements are another potential option to delay the progression of canine cognitive dysfunction. The primary goal with these therapies is to decrease free radical damage and increase antioxidant levels within the brain.
Hills Pet Nutrition has released a diet specifically formulated to address canine cognitive dysfunction. This diet, known as Canine b/d®, is supplemented with antioxidants and fatty acids, as well as other ingredients intended to improve mitochondrial function.
Studies have shown that the benefits of this diet can be apparent in as little as two to eight weeks; older dogs fed this diet for two years do better on a variety of cognitive function tests than control dogs who were not fed the diet.
There are a number of nutritional supplements that have been used in the treatment of canine cognitive dysfunction.
Phosphatidylserine is one such supplement. It is a membrane phospholipid, theorized to improve nerve conduction and stimulate the release of acetylcholine and dopamine. This supplement has been used in human medicine and is available for pets as the supplement Senilife®.
S-adenosyl-l-methionine (SAMe) has also been used for the treatment of cognitive dysfunction. It is thought to improve receptor function and cell membrane fluidity, while also increasing the production of glutathione (an antioxidant) and the turnover of noradrenaline, serotonin, and dopamine. Humans with Alzheimer’s disease have been found to be deficient in SAMe, lending further credibility to the use of this medication in cognitive dysfunction.
Other nutritional supplements that have been used to address canine cognitive dysfunction include the following substances:
- Ginkgo biloba is a free radical scavenger and MAO inhibitor. It improves cerebrovascular blood flow and enhances the activity of dopamine and serotonin. Studies indicate that it successfully treats cognitive decline in aging humans.
- Vitamin B6 is a cofactor in neurotransmitter synthesis.
- Vitamin E enhances effects of ginkgo biloba and neutralizes free radicals.
- Resveratrol protects against oxidative damage and reduces beta amyloid secretion.
In addition to the medications, diet, and supplements that are directly used to treat cognitive dysfunction, additional medications may sometimes be required to directly address the outwardly-visible clinical signs of cognitive dysfunction.
Dogs that are experiencing significant anxiety, for example, may benefit from anxiolytics such as fluoxetine, buspirone, or lorazepam. Night-waking can sometimes be addressed through the use of melatonin or pheromones.
Canine cognitive dysfunction prognosis
While canine cognitive dysfunction is not typically regarded as a life-threatening condition, it can have significant effects on quality of life and the human-animal bond. These impacts can lead to euthanasia of affected pets.
Early detection of canine cognitive dysfunction can allow time for therapies to be started before the human-animal bond has been significantly damaged. Therefore, owners of middle-aged and older dogs should always be asked about signs of canine cognitive dysfunction.
While canine cognitive dysfunction is part of the normal aging process, interventions can slow the progression of cognitive decline and improve the pet’s quality of life.
Cognitive dysfunction is a common condition in aging dogs. The clinical signs of cognitive dysfunction can be summarized with the acronym DISHA: disorientation, interactions, sleep changes, housesoiling, and activity changes.
If these signs are noticed, treatment can be initiated with a combination of behavioral interventions, medications, dietary changes, and nutritional supplements.
Work with clients to determine the most appropriate therapy for their situation and the most effective treatment for their individual pet.
Sources and additional reading
- Primm, K. 2016. New review helps illuminate cognitive dysfunction syndrome. Veterinary Medicine. Retrieved from http://veterinarymedicine.dvm360.com/new-review-helps-illuminate-cognitive-dysfunction-syndrome
- Landsberg, G. 2016. Think it’s dementia? Remember DISHA. Veterinary Medicine. Retrieved from http://veterinarymedicine.dvm360.com/think-its-dementia-remember-disha
- Landsberg, G. 2009. Preventing and treating cognitive dysfunction in senior pets. Presented at Central Veterinary Conference, Kansas City. Retrieved from http://veterinarycalendar.dvm360.com/preventing-and-treating-cognitive-dysfunction-senior-pets-proceedings
- Canine Cognitive Dysfunction Rating (CCDR) Scale. University of Sydney. Retrieved from http://rng.org.au/wp-content/uploads/2014/09/CCDR-scale-revised.pdf
- Salvin, H et al. 2011. The canine cognitive dysfunction rating scale (CCDR): a data-driven and ecologically relevant assessment tool. Vet J. 188(3):331-6
- DVM360 Staff. 2012. Spotlight on Research: Cognitive Dysfunction Syndrome. Custom Veterinary Media. Retrieved from http://veterinarycalendar.dvm360.com/spotlight-research-cognitive-dysfunction-syndrome-sponsored-virbac-animal-health