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Veterinary Forum February 2007 (Vol 24, No 2)

Identity theft: when senior dogs forget

by Marie Rosenthal, Patrick R. Gavin, DVM, PhD, Sebastien Kfoury, DVM

    Mitsy spends all night pacing and won't settle down to sleep. Rocky goes outside, stands in the middle of the yard, and stares at nothing; then he enters the house and urinates on the rug. Lady used to be very affectionate but now doesn't want to interact with her owners, and Max never goes to the front door to greet people anymore.

    Every day, worried pet owners approach their veterinarians about their senior dogs' changing behavior. Living with a senior dog can be as frustrating for owners as dealing with a puppy, but the relationship dynamics are different. When the behavior of a well-trained adult dog alters, it can be confusing to owners. The veterinarian must determine what is affecting this animal and explain it to the owner while developing a program that will help improve the pet's quality of life.

    This is not an easy task, experts agree. The changed behavior may be a result of cognitive dysfunction, but it also may stem from a physical ailment (see Signs of Canine Cognitive Dyfunction). It is the veterinarian's challenge to determine whether the altered behavior is caused by either or both because no laboratory tests definitively diagnose cognitive dysfunction.

    Limitless diagnostic differentials

    Memory, learning, and social interaction are important cognitive traits in a dog. As a dog ages, its brain size and chemistry change; the ventricles enlarge, neurons decline, and infarcts may develop. These changes can cause the neurologic degeneration called cognitive dysfunction. However, there is no test for this disorder, only learning and memory tasks that are exclusively available at research facilities. Many physical complaints, such as pain or incontinence, can result in behavioral changes that look like cognitive dysfunction. The diagnostic differentials are almost limitless.

    "Cognitive dysfunction is often a diagnosis of exclusion," says Debra F. Horwitz, DVM, DACVB, a veterinary behaviorist and Veterinary Forum Editorial Board member. "When an older dog shows a change in behavior, it should be subjected to a good medical workup, including some blood work looking at endocrine, thyroid, pancreas, liver, and kidney function and assessment of pain to make sure there is no metabolic reason for the behavior.

    "Almost any senior dog will have one or more concurrent problems, and if you treat and control them but are still left with clinical signs, you often can conclude that you have cognitive dysfunction. But frequently you are faced with multiple conditions at the same time," explains Horwitz, of Veterinary Behavior Consultations in St. Louis.

    Because there is no definitive test for cognitive dysfunction, it takes a good diagnostician to weigh all the evidence and find the cause and possible treatments, observes Gary M. Landsberg, BSc, DVM, DACVB, a member of the Forum Editorial Board who has studied the disorder. A veterinarian must question pet owners about changes in health or behavior at every senior care visit to be able to identify problems at the earliest possible onset. "You have to ask — and you have to get the owner to report the signs. Then, as a veterinarian you need to determine what medical conditions might cause these signs. Only after ruling out or diagnosing and treating any medical causes can you determine from the remaining signs whether you think cognitive dysfunction is the cause or one of the causes. Of course, as a pet gets older, there can be multiple concurrent problems," says Landsberg, co-owner of Doncaster Animal Clinic in Thornhill, Ontario.

    "So, it is the presence of behavioral signs and the absence of a medical cause that would point you toward cognitive dysfunction as a cause of some or all of the signs."

    Pain assessment and management are crucial to the workup, experts say. A dog that is in pain will behave differently than it normally would. It might be stiff and slow to move or unable to get into the proper position to relieve itself, or it might not want to be touched and may isolate itself from the family unit, which could break the human-animal bond that is so important. All of the experts agree — look for and treat the pain.

    Not Alzheimer's disease

    Many people compare cognitive dysfunction to Alzheimer's disease in humans. They even call it doggie Alzheimer's, but the diseases are different, experts say. "There are a number of similarities between cognitive dysfunction in dogs and the similar declines that occur in people with early Alzheimer's disease and brain aging," Landsberg clarifies, "but I don't want to imply that they are the same because dogs don't get Alzheimer's. They don't get the end stages of Alzheimer's in which there are neurofibrillary tangles and some of the dense proteins that accumulate; but other than that, the conditions are similar."

    William Milgram, PhD, from the University of Toronto, says that studying cognitive dysfunction in dogs has helped physicians find ways to treat Alzheimer's disease and other dementia disorders in human patients, which may be where the comparison began. "The dog is a model of Alzheimer's and dementia. There are similarities in a subset of aged dogs in terms of both the cognitive dysfunction that they show as well as the neuropathology that you see in patients who are affected by Alzheimer's disease. I would [say] that the dog is a model of it. You can use it as one way to study Alzheimer's disease," Milgram offers. "We think the aging beagle probably is as good a natural model as exists for testing drugs that will be used on Alzheimer's patients."

    Successful agers

    Horwitz says that animals, just as people do, suffer degrees of aging that affect their brain and functioning. Many dogs are successful agers, while others are not. No one knows why dogs or people age differently, although many researchers are trying to determine the associated factors (see The Aging Canine Population).

    "Before cognitive dysfunction is actually diagnosed, we often have cognitive decline, so research studies have been designed to show that dogs experience cognitive decline — a change in their ability to learn new tasks — as early as 7 or 8 years of age.

    "There really are three groups of dogs: There are dogs that are successful agers. They age well, they don't show any cognitive dysfunction, and they learn pretty much as young dogs do throughout their lives. Then there are dogs that are mildly impaired and show some cognitive changes over the course of their lifetime. Maybe their learning capacity is changed or their behavior activity is changed, but they function fairly well. And then there are dogs that we probably would designate as having cognitive dysfunction. These are dogs in which cognitive changes are really manifested by changes in behavior or interaction with the people they live with," Horwitz explains.

    More old dogs

    The aging canine population is becoming a big part of a veterinarian's practice. An article in JAVMA found that almost 16% of dogs owned in the United States are 11 years of age or older, and 31% of dogs are between the ages of 6 and 10. These figures don't surprise Ava Frick, DVM, a veterinary chiropractor and owner of Animal Fitness Center in Union, Mo. "We have the capacity to recognize diseases earlier on and do something about them," she offers. "It is not to say that we didn't always have dogs that lived a long time, but we are seeing a greater percentage of dogs living longer than they would have, and I think it is because of what is available for them."


    Although cognitive dysfunction cannot be cured, interventions are available that the veterinarian can suggest to improve the quality of life of these dogs and, some experts think, possibly delay the onset or progression of cognitive dysfunction if it is found and treated early enough. These programs combine nutrition, exercise, and enrichment, according to Milgram, who is also president and CEO of CanCog Technologies.

    "I think [these programs are] a good way to treat it," says Milgram, who has conducted many of the published studies on nutrition and enrichment. Using a cocktail of antioxidants, Milgram has shown "beneficial effects in older dogs over a 2-year period in terms of cognitive assessment.

    "We also had evidence that the antioxidants in part prevent or reduce the development of neuropathology or corrupt things that can happen to the brain as a process of aging. We have further evidence (and this has been reported but not published) that if you start these dogs on antioxidant-enriched foods early in life, they will delay the onset. Nutrition methods should be started earlier rather than later," he adds.

    As a result of these studies, several pet food companies market a senior diet that provides antioxidants and other supplements for senior health that a veterinarian can recommend. Frick, who uses a holistic approach, advises that the animal eat real vegetables. Milgram says that it is the combination of vitamins, minerals, and so forth that helps the animal, so it might be hard to determine the correct amounts that are needed. Frick agrees and says that if a holistic approach is used, the veterinarian must study nutrition. However, some owners might prefer this approach.

    Food, however, is not the only answer. Just as humans have learned about staying healthy and fit, the canine program has to include enrichment and exercise in addition to a special diet and supplements because different ­aspects of the program affect different areas of the brain. "They are complementary to the effects of nutrition," Milgram says. "[Food] does help, but nutrition and enrichment seem to act differently. One possibility is that cognitive exercises promote the growth of new cells in the brain or reduce the death of old cells, resulting in a neuroprotective effect."

    Landsberg says that laboratory experiments have implemented puzzles, such as "find the food," to measure a dog's cognitive impairment and to improve its memory. "Enrichment is using your brain, not just exercising: hide-and-seek games, where is the food, which hand is it in, ongoing training programs, food puzzles, and any activity you might think of to enrich your dog mentally."

    Owners can teach old dogs new tricks. In fact, helping a dog relearn a skill that it lost can improve its function. "You can reteach a dog, but it depends on the cause [of the lost learning]," Landsberg says. "You can improve some medical problems, others you can't. You can improve cognitive dysfunction in some of these animals, which means they can relearn their housetraining, but you still have to do the training."

    Coping mechanisms

    Horwitz says veterinarians should offer ideas for coping with a dog's dysfunction. For instance, a large problem for owners is that their pet starts soiling in the house. "Do not assume that the dog went when you see him on the porch. Instead, go outside with him and watch the dog. Go out and tell the dog to go potty," advises Horwitz, who adds that she used this technique with her own Labrador retriever, which lived to age 16. "As her decline worsened, we would walk her outside on a leash and make sure she went to the bathroom. Instead of letting her out to try to remember, we witnessed elimination, and she did not soil in the house because we made sure her bladder was empty," Horwitz explains.

    Frick says that the earlier the owner starts intervening, the better for the animal. "Early on, you want to improve the diet," she says, adding that exercise is also important because it stimulates the dog's senses as well as improves circulation. "We want to keep the circulation going, which keeps the body alert, and if dogs exercise during the day, they will be more likely to sleep through the night."

    Frick talks to owners about an overall program that deals with physical ailments, such as pain, as well as diet, including snacks, and exercise and enrichment. "Interaction is always going to help," she says. "Change the environment. Instead of staying inside the apartment, house, or yard, take them out of that space.

    "That will stimulate a part of the brain that has not been stimulated. Take the dog to places it hasn't been. Maybe it can't see so well, but I tell you that sniffer still works. Allowing it to experience stimulus from that perspective is very real to the dog," Frick says.

    Horwitz agrees. Just as the act of eating a Madeleine resurfaced childhood memories for Marcel Proust, a walk stimulates a dog's senses. Horwitz advises veterinarians to recommend a walk, even a short one. "Dogs find going for a walk to be an enriching experience, so they walk around their environment. They sniff their environment. They see different things, they encounter different people, and they get muscle stimulation. Recent articles have shown that exercise helps people to improve cognitive function because it increases blood flow.

    "So, by simply walking the dog, showing it some simple obedience tasks, and making sure the dog is fed a diet that is enhanced or augmented for a senior dog, are you going to be able to stop cognitive dysfunction from taking place? Not in dogs that are predisposed," Horwitz warns. "Are you going to be able to enhance the quality of their life throughout their lifetime? Certainly."

    Sometimes dogs need more than nutrition, exercise, and enrichment, but there is only one drug, selegiline hydrochloride (Anipryl, Pfizer Animal Health), that is approved for the treatment of cognitive dysfunction in dogs. No one could discuss whether other drugs approved in Europe are being researched for use here. Landsberg says that supplements designed for pets, such as those that contain DHA, phosphatidylserine, and ginkgo biloba, are also being tested and there are preliminary studies to support their effectiveness. Not everything that works in mice works in people, and not everything that works in people works in dogs, he continues.

    "Dietary and nutritional protocols may prevent or slow the decline of the disorder, while most drug protocols are useful at improving the clinical signs," says Landsberg. Milgram adds that cognitive dysfunction results from physical changes in the brain that affect memory and learning, and more research is being done to understand and help the disorder.

    Deal with the expectations

    It is important to let owners know that cognitive dysfunction cannot be cured, so veterinarians must discuss expectations with clients. Horwitz warns: "Cognitive dysfunction is a progressive disorder, so we are not going to cure it." But it can be managed, and that management can improve not only the life of the dog but also that of the owner.

    Caring for pets with cognitive dysfunction should be part of an overall assessment of a senior dog, Landsberg says. "The real key to senior care is not just focusing on cognitive dysfunction but helping owners to understand that, as pets age, ultimately something will go wrong. The earlier we find out, the more likely we are to have access to treatment and diets that may help," he suggests. "And most of the assessment, testing, and even treatments are not necessarily invasive. Sometimes it is as simple as changing the diet or adding a medication or supplement. So owners with older pets need to be told to visit their veterinarians more frequently, and they need to allow more frequent workups. Veterinarians must let owners know that we do have treatments that can improve the quality of life or even help older pets live longer and healthier lives."

    Horwitz says owners have to be told what is normal aging and what is not. "I think that it would be very useful to help owners understand that when their dog slows down or starts to behave differently, it is not necessarily normal aging. If we find some dogs when they are mildly impaired, we can increase their quality of life for quite some time with diet and medication and by making sure we treat all concurrent problems, as I did with my own dog. She was a fairly old Labrador retriever. Every step of the way as she was aging, as other problems started to emerge, we treated them. Taking care of the cognitive part of the senior dog health care is just as important as dental disease, twice-yearly blood work, and pain control. We want to encourage owners in this use-it-or-lose-it philosophy. We want to keep dogs active," she urges. "There is quite a bit of information out there that we can provide to owners."

    Although not as much is known about cognitive dysfunction in cats, Milgram says that is where researchers will start looking, and they will find many similar problems that are found in dogs.

    In fact, scientists at the Universities of Edinburgh, St. Andrews, Bristol, and California recently identified the same protein that causes tangles in Alzheimer's patients in the brains of aging cats. In humans, the tangles inhibit messages being processed by the brain, and the protein may lead to cognitive dysfunction in cats. Previous research had identified thick, gritty plaques on the outside of elderly cats' brain cells, which are similar to those found in humans.

    Twenty-eight percent of pet cats 11 to 14 years of age develop at least one age-related behavior problem, and this increases to more than 50% in cats that are older than 15.

    Experts suggest that the same factors used for dogs — good diet, mental stimulation, and companionship — can reduce the risk for dementia in cats.

    NEXT: Include new virus in the diagnosis of dogs with kennel cough


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