Dogs and people are similar in many ways. Their brains age in nearly parallel fashions. Older brains are not as speedy as younger ones, but in many, the slowing is pathologic. In humans we know this as dementia, or Alzheimer’s, a specific type of dementia. For dogs, and cats, we call it Cognitive Dysfunction Syndrome (CDS). Although our pets usually do not read the New York Times on a daily basis, their cognitive decline can be noted in the performance of daily tasks. The syndrome is characterized by a gradual cognitive decline and increasing brain pathology. Progression of clinical signs is very gradual, so gradual in fact that most owners fail to recognize it is happening.
Many behavior changes may occur with CDS. The most common is similar to people: the pet seems lost. You may find the dog wandering around, staring at walls, walking into a corner and not being able to turn around. Think of a person who goes to the grocery store, but cannot find their way home. Aging in pets may also lead to altered learning and memory. Previously known tasks may start to be forgotten, such as housetraining or fetching. Cats may stop using the litter box regularly; dogs may soil inside the house. Working dogs may show a decline in their abilities to perform well.
Many family members describe changes in social behaviors in people with dementia. Dogs and cats are no different. They may have fewer social interactions, play differently and can even fail to respond to people that they love. Although having decreased social interactions, they may have altered sleep-wake cycles such as night walking or increased anxious pacing. They may walk in circles for extended periods. Some pets will be uneasy in the dark, but settle when a light is turned on.
In people we can perform MRI scans along with cognitive testing to determine if dementia is present. This is not as straightforward in pets. Physiologically, there is a slow, but steady decrease in the total weight and size of the brain, especially in the cerebral and cerebellar regions. Increased accumulation of β amyloid plaques occur.
How β amyloid accumulation affects the development of cognitive dysfunction has yet to be determined, but it has been noted that the greater the β amyloid, the greater the impairment. There is also a decrease in certain neurotransmitters, molecules that relay information between brain cells, in older pets and humans. Other changes are also present. The problem is that in pets, we can only observe behavior changes, not physical changes in the brain. A diagnosis is based upon ruling out other reasons for behavior changes, such as pain (arthritis), high blood pressure, kidney disease, thyroid disease, brain tumor, drug reactions, other endocrine disorders, infections, etc.
About one third of cats 11 to 14 years of age develop at least one geriatric-onset behavior problem that appears to be related to cognitive dysfunction. The numbers for dogs may even be higher.
As of present we do not have a specific treatment to reverse CDS. Several medications, along with dietary changes, environmental management and supplements, may help with the clinical signs of CDS. Diets rich in antioxidants and omega fatty acids may reduce oxidative damage in the brain and can help reduce β amyloid production. Hill’s b/d is the most popular of the veterinary diets, and it has been shown to increase engagement and cognitive awareness.
Environmental enrichment is essential to helping keep a senior friend comfortable. In a previous article in Hill Rag, we discussed many modalities for stimulating elder brains. A quick summary follows. Regularly exercise your dog or cat. Walks are best as they introduce new smells to dogs and make their brains work. Attempt to teach new tricks or reinforce old ones. Simple puzzle games for food work well, too. Cats are less amenable to change in environment than dogs and restricting their space may be a benefit to cats with CDS. Smaller rooms for cats with readily available litter boxes and food may help them feel more comfortable.
Some dogs will respond to a medication called selegiline. It increases the availability of a certain neuro-transmitter, helping dogs be more cognitively aware. The medication can take up to a month to show any effects, although some pets are more responsive after a few days. Other pets may respond to fluoxetine, a tricyclic antidepressant medication.
Pets age, so do their brains. While there is no cure for cognitive dysfunction, pets can be assisted through diet, environmental enrichment, and medication. The best thing you can do to help your dog is to try and teach it a new trick.
Dan Teich, DVM is Medical Director at District Veterinary Hospital Eastern Market.
