Even a minor change in behavior
might be indicative of
underlying medical problems or
a decline in cognitive dysfunction.

It is not unusual for behavior problems to develop in older pets and often there may be
multiple concurrent problems. It is also important to note that some of the changes
associated with aging may not seem significant, but even a minor change in behavior
might be indicative of underlying medical problems or a decline in cognitive
dysfunction. Since early diagnosis and treatment can control or slow the progress of
many disease conditions, be certain to advise your veterinarian if there is any change
in your pet’s behavior.

What are some of the causes of behavior changes in senior

1. Many of the problems have similar causes to those in younger pets. Changes in the
household, changes in the environment and new stressors can lead to problems
regardless of age. For instance moving, a change in work schedule, a family member
leaving the home, or new additions to the family such as a spouse or baby, can have a
dramatic impact on the pet’s behavior. In addition, it is likely most older pets will be
more resistant or less able to adapt to change.
2. Older pets are also likely to develop an increasing number of medical and degenerative problems as
they age. Any of the organ systems can be affected and play a role in the development of a wide variety
of behavior problems. For example, diseases of the urinary system and kidneys can lead to house-
soiling. Diseases of the endocrine organs such as the thyroid gland and pituitary gland can lead to a
variety of behavioral and personality changes. A decline in the senses (hearing and sight), painful
conditions, and those that affect mobility may cause the pet to be more irritable or more fearful of
approach and handling (see handout on Behavior – causes and diagnosis of problems for more details).

3. As with other organs the brain is susceptible to age related degenerative processes that can affect the
pet’s behavior, personality, memory, and learning ability. When these changes occur, the pet may show
varying degrees of cognitive decline (discussed below) and in pets that are more severely affected, this
might be referred to as cognitive dysfunction or senility. Many of these changes are similar to what
occurs in aging humans. In fact, the amyloid deposits that are found in the brain of dogs with cognitive
dysfunction are similar to what is seen in the early stages of Alzheimer’s disease in people.

How can I find out why my pet’s behavior has changed?

Regardless of age, every behavior case should begin with a complete veterinary physical examination
and a clinical and behavioral history. In addition, blood tests and a urinalysis may be needed to rule
out organ disease and endocrine imbalances, especially in the older pet. Sometimes a more in depth
examination of a particular organ system may be indicated. Additional laboratory tests, radiographies,
ultrasound, spinal tests, brain scans, or perhaps a referral to a specialist may all be appropriate. A
decision on which tests are needed would be based on the pet’s age, previous health problems, any
ongoing drug or dietary therapy and an evaluation of all of its medical and behavioral signs and the
findings of the physical exam.

My pet is quite old. Is there any point in doing these tests?  What can be

Unfortunately many pet owners do not even discuss behavior changes with their veterinarians since
they feel that the changes are a normal part of aging and perhaps nothing can be done for their dog or
cat. This is far from the truth. Many problems have an underlying medical cause that can be treated or
controlled with drugs, diet or perhaps surgery. Hormonal changes associated with an under active or
overactive thyroid gland, diabetes, diseases of the pituitary gland and testicular tumors can all lead to
dramatic changes in the pet’s behavior and many of these problems can be treated or controlled.
Degenerative organ systems can often be aided with nutritional supplementation or dietary changes.
High blood pressure, cardiac disease and respiratory diseases may be treatable with medication, which
may dramatically improve the quality and even length of the pet’s life. And drugs and dietary therapy
are also available that are useful in the treatment of age related cognitive dysfunction.

What are some things to look out for?

Changes in behavior (see cognitive dysfunction below), an increase or decrease in appetite or drinking,
an increased frequency or amount of urination, loss of urine control (dribbling urine, bed wetting),
changes in stool consistency or frequency, skin and hair coat changes, lumps and bumps, mouth odor
or bleeding gums, stiffness or soreness, excessive panting, coughing, changes in weight (increase or
decrease), and tremors or shaking are some of the more common signs that should be reported, should
they develop in your pet.

What is cognitive dysfunction and how is it diagnosed?

It is generally believed that, as in people, a dog or cat’s cognitive function tends to decline with age. If
your dog has one or more of the signs below and all potential physical or medical causes have been
ruled out, it may be due to cognitive dysfunction. Of course, it is also possible that cognitive
dysfunction can arise concurrent with other medical problems, so that it might be difficult to determine
the exact cause of each sign. Over the past few years the signs commonly attributed to cognitive
dysfunctions have been described by the acronym DISH (Disorientation, alterations in Interactions with
family members, Sleep-wake cycle and activity level changes or House soiling). However this may not
be a sufficiently complete list to describe all of the categories in which a decline in cognitive function
might be seen. These might include:   

a)        Disorientation (such as getting lost in familiar areas such as the home or yard)

b)        Social interactions might be altered between the pet and owner or pet and other pets – some pets
may appear to be more clingy while others might be disinterested or even irritable when petted or

c)        Anxiety might be increased

d)        Activity levels often decrease so that the pet is seen sleeping more or less playful and
exploratory. However some pets also become more active and restless with pacing, or even stereotypic
behaviors such as licking or bouts of barking

e)        Appetite may be affected with some pets showing a disinterest in food and others having a more
voracious appetite

f)        Altered sleep cycles with increased waking or restlessness at night

g)        Altered learning or memory as demonstrated by an inability to retrain, loss of performance (such
as commands, working ability, or previous training) or house soiling (no longer can remember where
to eliminate or how to signal)

In one study of dogs that were 11-16 years of age, owners specifically questioned regarding signs of
cognitive dysfunction reported that 28% of 11 to 12 year old dogs and 68% of 15 to 16 year old dogs
exhibited at least one of the signs above. However, it’s important to note that these are signs noticed by
pet owners in comparison to when their dog was younger. Research has shown that if you were to try
and train your dog on some new learning tasks, that after about 8 years of age many dogs may begin to
show a decline in memory and learning ability around this age. Owners of older cats also noted many
of these signs listed above but they tended to arise at a little older age (e.g. 15 years and older)
Treatment options tend to be most effective at slowing or reversing decline when they are instituted
early in the course of disease. Therefore, be certain to report any of these signs to your veterinarian

Do pets get Alzheimer’s?

Many of the same changes and lesions associated with Alzheimer’s disease in people have also been
recognized in dogs and cats. Should multiple behavior problems develop and these changes progress
to the point where the dog or cat is no longer a “functional” pet, the condition may be consistent with
senility or dementia of the Alzheimer’s type.

Can geriatric behavior problems be treated?

In many cases the answer is yes. Of course if there are medical problems contributing to the behavior
changes, the problem may not be treatable. The key therefore is to report changes and bring in your pet
for assessment as soon as new problems arise.

Dogs that develop behavior problems due to underlying medical conditions may need alterations in
their schedule or environment in order to deal with these problems. If the condition is treatable and can
be controlled or resolved (e.g. Cushing’s disease, infections, painful conditions) then, as discussed, you
must be prepared to retrain the dog, since the new habit may persist. For example, the house-soiling
pet may have less duration of control due to its medical problems. If these conditions cannot be
controlled, then the pet’s schedule (more frequent trips outdoors), or environment (installing a dog
door, paper training) may have to be modified. With conditions that affect a cat’s mobility, adjustments
may be needed to the pet’s environment, litter box placement, or type of litter box, (e.g. A lower sided

In cognitive dysfunction, an increase in a neurotoxic protein called beta amyloid, an increase in
damage due to toxic free radicals, a loss of neurons, and alterations in neurotransmitters such as
dopamine may be responsible for many of the behavior changes. Both drug therapy and dietary
therapy are now available that might improve these signs and potentially slow the decline. Again early
diagnosis and intervention is likely to have the greatest effects.

Selegiline is a drug that has been licensed for the treatment of cognitive decline in dogs in North
America. It is classed as an MAOB inhibitor but its action may be to enhance neurotransmitter function
such as noradrenaline and dopamine, to help reduce free radical damage in the brain and perhaps as a
neuroprotective drug (see details in our handout on drug therapy). Many of the signs listed above
(DISH) may be improved by treatment with selegiline.

Another method of managing senior behavior problems is a prescription diet that is designed to
protect against and possibly reverse damage due to toxic free radicals. It is enhanced with a variety of
antioxidants including vitamin E, Selenium, vitamin C and fruits and vegetables. It is also
supplemented with essential fatty acids in the form of fish oils and some factors to help the cell’s
mitochondria function more efficiently including carnitine and lipoic acid. The diet has been shown to
improve learning ability and memory in old dogs and improve many of the clinical signs listed above
(i.e. DISH).

There are a number of other medications, some licensed for use in European countries (such as
nicergoline and propentofylline). These drugs have been developed for use in human geriatric
patients. They are behavior modifying drugs that might also enhance cognitive function by increasing
blood flow through the brain or by enhancing neurotransmitter function.

It is important to note however that once new habits are learned, retraining and changes to the
environment may also be needed to resolve the problem. For example, in addition to drug therapy,
dogs that have begun to eliminate indoors will need to be retrained much like a puppy that has begun
to eliminate indoors.

This client information sheet is based on material written by Debra Horwitz, DVM, DACVB and
Gary Landsberg, DVM, DACVB. © Copyright 2002 Lifelearn Inc. Used with permission under license.
October 31, 2007.
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