Too often just dismissed as “old age,” canine cognitive dysfunction has specific symptoms and treatments.
Is it natural for older dogs to gradually lose energy and interest in life? Some of these behavioral changes are predictable and may be linked to aging, but others should be attended to; they could be symptoms of canine cognitive dysfunction syndrome.
CDS is an age-related deterioration of cognitive abilities characterized by behavioral changes. It’s sometimes referred to as “old dog syndrome” or “senility.” The symptoms are wide-ranging and can be associated with other medical conditions, making CDS tricky to diagnose.
Many pet owners assume that nothing can be done when their dogs begin exhibiting senility. A recent study revealed that only a small percentage of dog owners who noticed behavior consistent with CDS reported it to their veterinarian. Often, behavioral changes are written off as a normal part of aging. This isn’t necessarily the case.
Just because CDS is common doesn’t mean it’s normal. “People will often comment that their older dog is acting senile, as if it’s to be expected,” says Curtis Dewey, DV M, M.S., associate professor and section chief of neurology/neurosurgery at Cornell University’s College of Veterinary Medicine in Ithaca, N.Y. “It’s not normal to be senile, even for a dog.”
What is CDS?
CDS is strikingly similar to Alzheimer’s disease in people. It’s caused by chemical and physiological changes in the brain. A cluster of symptoms may be noted, such as confusion, memory loss and personality changes. The signs of CDS are progressive and gradual, so many dog owners fail to recognize the early stages.
In a clinical study conducted in the late 1990s by the University of California, Davis, School of Veterinary Medicine, 62 percent of 11- to 16-year-old dogs showed at least one sign of cognitive decline. In a separate pet-owner survey conducted by the drug manufacturer Pfizer Animal Health in 1998, nearly half of dogs age 8 and older showed at least one symptom associated with CDS.
Dogs with CDS show behavioral changes that are not a normal part of aging. “A lot of dogs with CDS will forget which side of the door to go to and will stand at the hinge side rather than the side that opens,” Dewey says. “[Normal] dogs rarely make that mistake.”
Other behavioral changes include house-training problems, apparent memory loss, wandering, becoming “stuck” in corners, sleep disturbances and restlessness. Sometimes, the changes may seem contradictory, such as a dog that has symptoms of hearing loss, but also seems more sensitive to strange sounds.
Before any medical signs become apparent, these types of behavioral changes may indicate that something is changing in an older dog. “CDS is a diagnosis of exclusion in which all other diseases and medical conditions are ruled out,” says Melissa Bain, DVM, Dipl. ACVB, M.S., of the Companion Animal Behavior Service at UC Davis. Primary and secondary behavioral problems, such as noise phobias and separation anxiety, need to be ruled out before diagnosing CDS.
If a dog is suspected of having CDS, veterinarians typically ask the owners to complete a form that details the history of their dog’s behavior and routines. The checklist collects information on the dog’s appetite, elimination patterns, cognition, recognition, social relationships, sleep-wake patterns and anxiety. This type of questionnaire, a physical and neurological exam, and diagnostic tests are necessary to make an accurate diagnosis of CDS.
Necropsies performed on dogs with CDS show their brains are frequently clogged with globs of nerve damaging beta-amyloidal plaque, similar to what is found in the brains of people with Alzheimer’s disease. “The type of amyloid [protein] is the same in both dogs and people”’ says Andrew Farabaugh, DVM, staff neurologist at MSPCA-Angell Animal Medical Center in Boston. “Because of this similarity, dogs are being used as experimental models for Alzheimer’s research.”
Necropsies of dogs diagnosed with CDS also reveal increased levels of monoamine oxidase B (MAOB). Monoamine oxidases are enzymes found in different parts of the body: MAOA is found in the liver, gastrointestinal tract and placenta; MAOB is mostly found in blood platelets. Both forms break down neurotransmitters (chemicals that enable nerves to communicate), one of them being dopamine.
Because of the vital role that MAOs play in the inactivation of neurotransmitters, MAO dysfunction (too much or too little MAO activity) is thought to be responsible for a number of neurological disorders in the brain, as well as a depletion of the neurotransmitter dopamine – important because it connects thought with action, and increases cognitive awareness. All of these conditions tend to accelerate degeneration of the brain.
Researchers have not determined a genetic cause for canine dementia, nor can they explain why some dogs are afflicted with CDS and others are not. “Similar to people with Alzheimer’s disease, there is no way to show which dogs will eventually develop the disease,” Bain says.
CDS is incurable and usually progressive in nature. Once diagnosed, however, several options are available to manage the disease. A combination of drug therapy, dietary changes and environmental stimulation can help a dog maintain an optimal quality of life.
Anipryl (L-deprenyl), manufactured by Pfizer Animal Health, is the only FDA approved drug currently on the U.S. market for managing CDS. Anipryl prolongs the concentration of dopamine in a dog’s brain (by inhibiting MAOB, increasing the amount and effectiveness of dopamine), and reduces the free radicals naturally produced by the body. Some age-related behavioral changes in older dogs are thought to be caused by free radical damage to the brain. With higher levels of dopamine, many cognitive processes are augmented.
In Pfizer and UC Davis studies, 69 to 75 percent of dogs showed some improvement on Anipryl after one month of treatment. Some dogs continued to show improvement for up to three months. These findings were based on observational information collected from owner-reported questionnaires. “Any observational report, though, is going to be fraught with problems because of the placebo effect.” Farabaugh says.
Specific questions can be asked and standardized tests can be given to humans with Alzheimer’s disease to determine how a patient is progressing. With dogs, it’s different. “We judge an animal’s cognitive dysfunction by how much they move around,” Dewey says. “People will say their dogs are better simply because they seem to be more alert and more active.”
Anipryl is given in tablet form in low doses; side effects are minimal. “Overall, it’s a pretty harmless drug,” Bain says. “The earlier Anipryl is started, the better the result.” Some common side effects include gastrointestinal upset, vomiting, salivation and agitation.
Dog owners need to be aware of certain drug interactions, especially if a dog is already taking narcotics. “Tramadol is a drug that has become popular for managing pain in older dogs,” Farabaugh says. “The risk from tramadol is not particularly significant according to some veterinarians, but I would avoid [using] tramadol and Anipryl together, if possible.”
Other medications require a withdrawal period of several weeks before starting a dog on Anipryl.
Some documented studies indicate that dietary changes and supplemental intake for older dogs can improve the performance of cognitive tasks, suggesting a specialized diet can be more beneficial than a regular diet.
“Diet can have a strong influence in slowing the symptoms of CDS,” Bain says. Hill’s Prescription Diet b/d Canine (the b/d stands for “brain diet”) is specially formulated to fight age-related behavioral changes in older dogs. “This particular product has a high concentration of antioxidants, essential fatty acids and mitochondrial factors,” Bain says. “ Because it’s a balanced diet, there is no harm in trying it.”
Farabaugh adds that the best time to start b/d Canine is before your dog shows any clinical signs. “You’re not going to undo a lot of the damage once it occurs; you’re just going to slow it down,” Farabaugh says. “Unless there are [more pressing] dietary needs to consider, starting a dog on the b/d diet once it’s 7 or 8 years old would, in theory, decrease the risk of developing dementia.”
Supplements and nutraceuticals
Other studies show that adding vitamins E and C, fish oil and DHA (docosahexaenoic acid) to the diet have varying success in slowing down the symptoms. “Ginkgo biloba is another supplement that’s often used because it decreases oxidative damage,” Farabaugh says. “It’s a monoamine oxidase inhibitor [MAOI] that may protect against some cell death, increases vascular flow and has an antioxidant effect.”
Nutraceuticals are another option to consider when treating canine cognitive dysfunction. The term nutraceutical was derived from the words “nutrition” and “pharmaceutical” in the late 1980s. It’s a food or part of a food that provides medicinal or health benefits, including the prevention or treatment of a disease. Several nutraceuticals to treat CDS are available without a prescription, including Senilife by Ceva Animal Health, Geri-ACTIVE by Centaur VA Animal Health (Canada), Senior Moment by Nutramax Laboratories and ProNeurozone by Virbac. Most of these products contain phosphatidylserine, a naturally occurring phospholipid, which is a major building block in cell membranes that improves cognitive function.
A third approach in delaying the progression of CDS is to keep your dog mentally and physically stimulated. “Novelty and change tend to have a positive impact on dogs,” Farabaugh says. Regardless of age, it’s possible for dogs to learn new things and improve the quality of their lives.
Dogs that engage in regular exercise and extra playtime appear to have less cognitive dysfunction. “[Researchers] have found in people that it’s not so much using your memory, but learning new things that slows the progression of memory loss,” Farabaugh says. “Learning a new language or skill is more beneficial than just trying to memorize a list of words. The same applies to dogs. Teaching them new tricks has definite value.”
An enrichment program that includes playing with mentally challenging toys and interacting with other dogs and animals also contributes to improving a dog’s learning ability. Increased activity, curiosity and thinking will usually improve the overall behavior of dogs with CDS.
When to seek help
The population of geriatric dogs is growing steadily, mirroring the increase in the human elderly population. “What we’re finding is the more we know about our pet’s healthcare, the longer they live and the more we tend to see these age-related issues that were never really a problem 30 or 40 years ago,” Farabaugh says.
CDS is not a normal part of aging and its symptoms are not easily identified during a routine veterinary examination. Because they are most familiar with their dogs’ habits and behavior, owners of senior dogs should look for subtle signs of the disease.
“People shouldn’t just say, ‘My dog is getting old,’” Bain says. “If you see even the slightest signs of CDS, seek treatment and advice from your veterinarian. Chances are a dog will continue to develop more severe symptoms over time.”
With a little extra care and attention, older dogs can be helped to manage their cognitive changes and spend their golden years enjoying a full and active life.
Symptoms of CDS
The most common signs of cognitive dysfunction syndrome can be grouped under the acronym DISH: disorientation, interaction with others, sleep-cycle changes and house soiling. It’s unusual to see all four symptoms in the same dog; a diagnosis can be made on the basis of only one of these categories:
- Not able to recognize previously familiar people or places
- Becomes “stuck” in corners or behind furniture
- Appears lost or confused in house or yard
- Forgets or stops responding to its name
Interaction with others
- Seeks attention less often
- Grows less tolerant of being petted (wanders away)
- Displays a lack of interest in surroundings or events
- Shows little familiarity upon greeting
Sleep and activity
- Sleeps more throughout the day
- Sleeps less at night
- Has reduced activity in a 24-hour day
- Increases wandering or pacing
- Loss of bladder and bowel control indoors
- Housetraining habits seem undone
- Signals less often to go outside
- Appears to forget reason for going outdoors