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Behavior Problems in Senior Dogs

Debra F. Horwitz DVM, Diplomate ACVB
Veterinary Behavior Consultations
St. Louis, Missouri

As companion canids age, they undergo both physical and metabolic changes that affect most body systems. These physical and metabolic changes can often manifest themselves as alterations in behavior. Each body system can result in differing and/or overlapping metabolic and behavioral abnormalities. Older pets are often seen in behavior practices, but the case distribution may differ from younger animals with separation related problems, destruction and house soiling being more common among older pets 1.

Physiologic changes associated with aging in dogs

The geriatric dog undergoes many physical changes as time passes. Within the musculoskeletal system these changes can be profound. Older dogs will experience arthritis of their joints and/or spondylitic changes in the spine and a decrease in muscle mass. These will all affect the mobility of the animal. Geriatric dogs also experience alterations in the visual system. The most common change is nuclear sclerosis. Additionally, the formation of age related cataracts could result in a functional vision loss that owners will notice 2. Changes in the central nervous system include a decrease in white and gray matter 3. Neurotransmitter function changes with age; monoamine oxidase levels are altered, as are serotonin, dopamine and acetylcholine levels. Change occurs in neurons and dendrites. Oxygen levels in the brain of geriatric dogs are lowered 4. Decreases in special senses are also evident in geriatric animals. Deafness in geriatric dogs is usually due to degeneration of peripheral acoustic structures and not due Central Nervous System dysfunction 5. Changes in taste have also been noted in older dogs. Both the digestive and respiratory systems are affected in geriatric pets.

It is now believed that cognitive function declines with age in older dogs. Brains of older dogs were found to have neuropathologic lesions similar to those seen in people with dementia. The cognitive changes associated with aging in dogs have been called Cognitive Dysfunction Syndrome (CDS) 6. The signs most often associated with CDS are: decreased reaction to stimuli, confusion, disorientation, decreased interaction with the owners, increased irritability, slowness in obeying commands, alterations in the sleep-wake cycle, decreased responsiveness to sensory input and problems in performing previously learned behaviors such as house-training9.

All of these physiologic changes can result in behavioral changes in an older pet. Changes in the animal's joints can often be accompanied by pain. Some dogs show very little evidence of pain, while others become irritable. This irritability can lead to aggressive encounters with family members and visitors 7. Medications can help decrease pain and therefore increase the dogs' ability to interact with people. Accommodations in sleeping arrangements and walking surfaces need be considered to maximize the dog's comfort and minimize pain.

Visual and hearing loss can result in danger to geriatric pets in new environments or when running loose outside. Hearing loss can make animals less aware of people approaching resulting in the animal being startled and possible aggressive responses. Loss of smell or taste may result in a decreased interest in food. Abnormalities of the digestive system may result in diarrhea or constipation with possible house soiling. Changes in neurotransmitters may result in dogs that are less socially active, slower to obey commands and less alert to their surroundings.

Diagnosis of behavior problems

Behavior problems in older pets often have underlying metabolic complications, which may be treatable. Older pets are valued family members and anything that can be done to make their remaining time with their family more pleasant is appreciated, medically sound and good veterinary medicine. Thorough physical examinations and medical work ups with appropriate laboratory tests are essential in geriatric pets with behavior problems. Once all medical problems have been identified and/or treated, then the behavior problem can be addressed. However, metabolic alterations may be chronic and continue to contribute to behavioral abnormalities.

As in any behavior case, a complete history is essential. A history should help identify the motivation for the behavior and circumstances that contribute to its occurrence. Attempts should be made to determine the origin of the problem, duration and progression of the problem behavior. Determine when and where the behavior problem occurs. The people involved with the animal on both a daily basis and with the behavioral problem should be noted. Routine interactions should be explored and any changes in routine examined. Some problems may have been present for the entire time they have owned the pet but are now being exhibited differently, or more frequently or more intensely than in the past.

Treatment of behavior problems in senior dogs

A vigorous attempt to rule out medical problems that may be occurring with behavioral disorders is extremely important in geriatric pets. Identification and treatment of underlying medical problems will allow the clinician to concentrate on changing the behavior. The same treatment modalities that are used in treating younger animals with behavior problems apply to geriatric pets. These include behavior modification (habituation, counter conditioning and desensitization) to alter the pet's behavior, modifying the environment, client education, pharmacological intervention and possibly surgery. Changes in physiology may alter how geriatric pets respond to these treatment modalities. Central nervous system changes may impair the rate of learning and the response to behavior modification. Altered metabolism in the liver and kidney may affect responses to drug therapy or preclude their usage. Physical limitations may prohibit or require certain environmental manipulation.

Common Behavior Problems in Senior dogs


Recent onset aggression in older dogs can often be due to underlying painful medical conditions. Among those that need to be considered are arthritis and dental disease. Lack of sensory input due to loss of vision or hearing can also result in aggression if the animal is startled. When an older dog has decreased mobility it effects how they may react to stressful events. While previously the dog may have left the situation, a lack of mobility or unwillingness to move may require the dog to stay. This may then result in a fearful situation for the dog that could result in aggression. Carefully monitoring interactions with visitors or young children is important. The dog should be watched for signs of stress or fear. If the dog shows any of these reactions, then remove the dog from the situation for safety. For fearful aggression, counter conditioning and desensitization programs can be developed to teach the dog how to respond appropriately in previously fearful situations. Head halters can be effect for additional control, and basket muzzles may be warranted in some situations.

Even at an elderly age, some aggression can be due to dominance aggression. Where previously the dog may have controlled the family with threats such as growling or snarling, these may escalate to snapping and/or biting. In other situations the pet may have expanded the challenge to family members to include new situations. The owner needs to learn how to establish a dominant position over their pet. The use of obedience exercises, control of resources, desensitization, headcollars and counterconditioning can be helpful. In some cases selective serotonin re-uptake inhibitors may be a useful adjunct to treatment if no underlying medical conditions contraindicate their usage.

Intradog aggression

In multi-dog households there usually exists a social structure with one dog as the dominant animal although dominance can be context dependent. This often can be the dog that was there first, usually the older dog. As a dog ages, and a young companion matures, there can be dominance challenges from the young dog to the older dog. When size is a compounding factor, serious damage can occur. An older dog may have to relinquish its dominance role to the younger, stronger and bigger dog. This could cause serious injury if the older dog will not relinquish the position or the owners insist on supporting the older dog as dominant while punishing the younger dog.

Treatment is aimed at either supporting the younger dog by allowing it to have first access to all resources such as owner attention, food, toys, outdoors. If this does not seem to resolve the problem, the owner needs to become dominant in all situations by totally controlling the interaction of the dogs. This is best done with headcollars and strict control using sit and/or down stay commands. The owners then control what dog gets what on a rotating basis. Close supervision and separation when no one is home or watching the dogs may be necessary to avoid injury.

Another area of intradog aggression is between an older dog and a new puppy in the home. New puppies are very energetic and playful. Play such as running, chasing, play biting and attacking can be annoying to an elderly dog. If the puppy will not respond to the threats and inhibited bites of the older dog, problems can result. These can range from overt aggression toward the puppy to hiding, anxiety, anorexia, housesoiling, vocalization and destruction by the older dog.

Treatment consists of careful monitoring of the interaction between the older dog and the new puppy. Intervention prior to aggression is preferred. Allowing the puppy vigorous play elsewhere before interaction with the older dog is helpful. Leash control of the puppy and reprimands for inappropriate behavior can teach the puppy control.

House soiling

House soiling can be a major problem in geriatric dogs, and one that frustrates owners. Kidney function declines with age due to changes in the number of nephrons, perfusion and reduced concentrating ability of the kidneys 8. There is also evidence that the decline in kidney function is related to changes in brain neurotransmitters, plaques and loss of neurons in elderly dogs resulting in loss of house training.1

Concurrent medical problems need to be investigated to rule out metabolic causes of urinary incontinence or inappropriate elimination. Different endocrine abnormalities may cause increased thirst and concurrent increase in urination. Medications that cause polydypsia and polyuria may also result in house soiling. For some older dogs, an increase in the frequency of access to outside is helpful in controlling elimination indoors. If the dog must be left for long periods, paper training may be helpful. Often owners resort to isolation of the dog to avoid ruining household possessions. This can lead to other problems such as loneliness or barking for attention. One possible solution is to keep the dog on a leash while with people so that the dog cannot wander off and eliminate and can alert people to its' need to go outside. For other animals a standard program of confinement and supervision can help retrain the pet. Naturally adequate cleaning of previously soiled areas is necessary to prevent odors from causing the dog to return to the location.

Defecation can also be a problem due to loss of sphincter control. Dogs will also respond to stress with house-soiling of stool. If the stress can be identified, the animal can be acclimated to the change and hopefully the house-soiling will subside. Changes in diet, either in type or frequency of meals can alter defecation routine and lead to house soiling.

Mobility problems can often be manifest by house soiling if the animal is unable or unwilling to get to the usual toileting area. Stairs, slick surfaces, change in surfaces may all be reasons that dogs with painful musculoskeletal problems may soil inside the home. Changes in the environment such as ramps, area rugs, additional grassy areas may help the dog to eliminate in the correct area. Dogs that are blind may have problems if relocated to a new home.

Separation anxiety and noise phobias

Changes in routine can also result in separation related distress. Signs include distress at being separated from the owner, vocalization, elimination and destruction. Treatment is aimed at changing the pet/owner interaction to one that is less dependent. Habituation to the leaving routine and planned departures designed to teach the dog to be left alone are used to treat separation distress.

Some geriatric dogs experience an increased sensitivity to noises such as thunder. Often dogs that exhibited low level anxiety to thunderstorms when younger will progress to showing severe phobic responses as they age. Counter conditioning and desensitization is the treatment of choice but often difficult to implement. Other treatment modalities include limiting exposure to the stimulus, and pharmacological intervention with tricyclic antidepressants, long acting benzodiazepines or SSRI's may be helpful. Naturally drug selection must be based on the medical status of the pet and laboratory testing prior to usage is recommended. Dosages and side effects are discussed in other sources1.

Cognitive Dysfunction Syndrome

Many clinicians now believe that cognitive function declines with age in older dogs 9. CDS is defined as "age-related or geriatric onset behavior changes that are not attributable to a general medical condition, such as neoplasia or organ failure"9. This cognitive decline may be manifest as behavioral changes in: house training, interest in food, attention and activity, awareness of surroundings, compulsive behaviors, circling, tremors, changes in sleep patterns, stiffness or weakness and inappropriate vocalization 10. In dogs, the neuropathological changes in the brain of an elderly dog are similar to those seen in humans with some forms of dementia 11. These changes consist of amyloid plaques, which seem to inhibit neuronal function. In addition, the amount of beta amyloid accumulation seems to correlate with the extent of cognitive decline11,   �12. Examples of behavior problems that may occur from these types of changes include separation related behaviors that are new or increased, uneasiness with visitors, disturbances in sleep wake cycles, house-soiling and other problems that were discussed earlier in this article. Usually these can be divided into 4 categories of behavioral change 1) Changes in the sleep-wake cycle; 2) reduction in social interactions; 3) loss of house-training; and 4) disorientation 13 . In addition, the prevalence of CD increases with increasing years with nearly 100% of 16-year-old dogs showing at least one category of behavioral change13.

Diagnosis of Cognitive Dysfunction Syndrome

Diagnosis of Cognitive Dysfunction Syndrome can be challenging. In an ongoing demographic study at the University of California at Davis researchers investigated the incidence of signs associated with CDS in dogs age 11-16 years (cited in)13. They found that 62% of 11-16 year old dogs scored positively for one or more behavioral categories commonly associated with CDS and listed above (cited in)13. Furthermore, the older the dog was, the greater the prevalence of signs with nearly 100% of dogs 16 or older showing at least one sign13. However, in surveys of veterinary practitioners only 7% of pet owners of senior dogs presented for routine health and vaccination reported signs of CDS without prompting9. This then implies that veterinary intervention and questioning are necessary to diagnose CDS in the dog especially in the early stages.

Frequent behavioral monitoring by veterinary health personnel can help identify CDS in the early stages. This can be accomplished by investigating potential medical and neurological disease and serial questionnaires designed to target specific areas of cognitive change. Dogs should be considered a senior patient when they become 7 years of age. At that time the owner can fill out a behavior checklist (available from Pfizer Animal Health) which can serve as a baseline measure of the dog's behavior and is filed with the patient record. At subsequent visits the owner can fill out the checklist again. If subtle changes are occurring they might become obvious to both the owner and the clinician over time.

CDS should be considered a possible diagnosis after a complete medical and nuerological work up that eliminates other potential causes of behavioral change. As mentioned earlier many medical and endocrine conditions may cause behavior to change in senior dogs. Examination for arthritis and possible neurological disease in this case has been discussed earlier in this article. Pertinent laboratory testing for this case has also been outlined above.

A behavioral history is then needed to make a diagnosis of CDS. Care should be taken to question about all areas of the owner-pet interaction including a what happens in a 24-hour day, an aggression screening and other behavior problems that may be occurring concurrently. The progression, duration, frequency and severity of the problem behavior(s) should be assessed. The most prevalent behavior problems seen in senior dogs over 9 years are: separation anxiety, aggression, phobias, house-soiling, compulsive disorders, waking or restlessness at night 14,   �15. To verify CDS the owners may need to be asked specific questions about behavior changes in the earlier mentioned categories. Examples include: Disorientation: questions on the dog getting "lost" or confused in the house or yard, a change in ability to recognize familiar people or places. Activity: sleeping excessively during the day but up at night. Interactions: a change in greeting family members, differences in soliciting attention. Housetraining: elimination indoors, loss of signaling need to eliminate 16. Other signs may be possible and volunteered by owners. CDS may occur concurrently with other behavior problems most notably an increase in separation anxiety, noise phobias and house-soiling.

It is now thought that changes in brain neurotransmitters, especially dopamine contribute to the cognitive decline in senior dogs16. The enzyme Monoamine oxidase B is responsible for the breakdown of dopamine and levels of MAOB are increased in the brains of elderly dogs. Selective monoamine oxidase inhibitors, especially those which target MAOB and hence dopamine breakdown, improve behavior of dogs experiencing CDS6. It is speculated that these medications aid in normalizing dopamine levels. In Canada and the United States a selective MAOB inhibitor, selegiline (AniprylPfizer Animal Health) is approved for use in dogs and has been shown to improve cognitive function as well as being a treatment option for Canine Cushings disease. In addition, selegiline may also have neuroprotective effects and decrease free radical load in the brain by decreasing free radical production.1

When treating dogs with CDS, treatment should focus on two areas. First, an attempt should be made to normalize neurotransmitter levels (dopamine, serotonin, norepinephrine and acetylcholine). Second, attempts to slow down the progression of the disease are helpful. Drugs available for use in dogs that normalize neurotransmitter levels or change the progression of the disease are limited. In Europe, treatment with Nicergoline has shown improvement in behaviors associated with senility 17. Nicergoline has alpha-adrenergic effects that increase vasodiliation, cerebral circulation, and stimulates metabolic activity of higher CNS centers17. In North America, selegiline (Anipryl Pfizer Animal Health) has been shown to help dogs with CDS by decreasing dopamine depletion, enhancing catecholamine activity and slowing neurodegeneration9.

Naturally any concurrent medical or neurological conditions should be identified and treated using physical examination and appropriate blood chemistries. Because of the age of the animals involved in cognitive dysfunction, multiple conditions most likely coexist and complicate both treatment and treatment response.

The drug selegiline (Anipryl) Pfizer Animal Health) is licensed in the United States and Canada for use in dogs for pituitary dependent hyperadrenalcorticism as well as for the treatment of Cognitive Dysfunction Syndrome. Selegiline is an irreversible monamine oxidase inhibitor and in dogs enhances levels of brain dopamine, phenylethylamine and plasma levels of amphetamine 18. In addition to these actions, selegiline effects the metabolism of free radicals in the brain by decreasing free radical production through inhibition of MOAB1. Free radicals damage cell membranes and DNA and their decrease may help slow the aging process. Lastly, selegiline may also exert neuroprotective effects and decrease cell death1. Recently selegiline has been demonstrated to prolong lifespan in dogs 10-15 years of age when maintained for the rest of the dogs life, but not less than 6 months 19.

Prospective clinical trial by Ruehl et al10 evaluated the safety and efficacy of selegiline for treatment of cognitive decline in dogs. Dogs 7-19 years of age were administered selegiline in an open label trial at .5mg/kg once daily. After one month, the population showed improvement in cognitive functioning. Recently a placebo blinded study again evaluated the treatment of Cognitive Dysfunction Syndrome in dogs with selegiline 20.

Once a diagnosis of CDS is made and appropriate medical evaluations administered, treatment with selegiline (Anipryl) may be initiated at a dose of 0.5-1.0 mg/kg once daily in the morning1. Morning administration is preferred to help combat changes in sleep-wake cycles and utilize increase plasma levels of amphetamine to keep the dog awake during the daytime hours18. Improvement in cognitive function is often noted in 2-4 weeks, with some pets not improving until into the second month of treatment. Changes in behavior may be subtle, owners are encouraged to keep journals to assess behavioral change. The response to therapy varies according to the degree of cognitive decline at initiation of therapy, duration and severity of brain pathology and naturally the environment and concurrent medical and behavioral conditions. Evaluation of response to therapy can be accomplished using behavioral questionnaires. The behavioral history should have identified target problem behaviors and the owner should watch for changes in frequency of those behaviors. For example, if the dog is housesoiling, then a decrease in indoor elimination and increase signaling to go outside may be noted. In other cases, the pet may begin to again greet family members when they return to the home. In dogs that were extremely restless during the night, less nocturnal restless behaviors and increased sleep may be noted.

Although no adverse reactions were reported during the drug trial to various antibiotics, anthelminthics, heartworm medications, analgesics, and antihistamines veterinarians should stay informed of all medications that the pet is concurrently taking1. The use of ephedrine, other monoamine oxidase inhibitors, tricyclic antidepressants, SSRI's, meperidine and opiods is contraindicated1. Selegiline is contraindicated in those with hypersensitivity to the drug. Care should be taken to avoid amitraz and Mitaban due to their monoamine oxidase inhibiting effects1. At least 14 days should be allowed between discontinuation of treatment with selegiline and treatment with a tricyclic antidepressant1. At least 5 weeks should be allowed after discontinuation of Fluoxetine treatment (Prozac) and initiation of treatment with selegiline1. In humans, concurrent use of MOA inhibitors and alpha 2 agonists has resulted in extreme flucuations in blood pressure therefore, blood pressure monitoring is suggested when the two are used together in dogs. Recommended dosages should not be exceeded. Severe toxicity and death in humans has been associated with the use of selegiline and TCA's (tricyclic antidepressnts such as Elavil) and SSRI's (such as Fluoxetine {Prozac}). The most common side effects seen during drug trials were vomiting, diarrhea and changes in behavior usually hyperactivity. Because of the age of most dogs placed on Anipryl side effects may be associated with other underlying disease states. Naturally, senior dogs require frequent monitoring and examination for ongoing disease processes.

Many changes take place both physically and behaviorally as a dog ages. By attending to the needs of senior pets, we can serve our clients well. One way to do this is to include questions about behavior in all veterinary visits. Often behavioral changes are the first signalment of disease. With good veterinary care, and attention to behavioral disorders, geriatric pets can live a long and comfortable life.


1.  Landsberg, GM, Ruehl, W. �Geriatric Behavioral Problems�, Veterinary Clinics of North America: Small Animal Practice 27:6 (November 1997) 1537-1559.

2.  Fischer,C. "Geriatric Ophthalmology," Veterinary Clinics of North America: Small Animal Practice 19:1 (January 1989): 103-123.

3.  Fenner, W. R., "Neurology of the Geriatric Patient," Veterinary Clinics of North America: Small Animal Practice, 18:3 ed.: 711-724.

4.  Mosier, J. E., "Effect of Aging on the Body Systems of the dog," Veterinary Clinics of North America: Small Animal Practice, 19:1 ed.: 9-11.

5.  Sorjonen, D. C., "Neurologic and Otologic Disorders of Geriatric Patients," Veterinary Clinics of North America: Small Animal Practice, 19:1 ed.: 131-132.

6.  Ruehl, WW, �Canine Cognitive Dysfunction as a Model for Human Age related Cognitive Decline, Dementia and Allzheimer's Disease: Clinical Presentation, Cognitive Testing, Pathology and Response to L-deprenyl Therapy� Prog. Brain Res. , 1995

7.  K. Houpt, B. Beaver, "Behavioral Problems in Geriatric Dogs and Cats," Veterinary Clinics of North America[Small Animal Practice] 11:4 (November 1981): 643-652.

8.  Krawiec, D.R., "Urologic Disorders of the Geriatric Dog," Veterinary Clinics of North America: Small Animal Practice, Vol.19, no. 1 ed.: 76.

9.  Ruehl WW, Hart BL, Canine Cognitive Dysfunction. Pharmaocology of Animal Behavior Disorders( Dodman NH, Shuster L, eds), Boston, Blackwell Science, 1998. pp.283-304.

10. Ruehl W., DePaoli AC., Bruyette D S., L-Deprenyl for treatment of behavioral and cognitive problems in dogs: preliminary report of an open label trial. Applied Animal Behaviour Science [abstract] 32(2) 1994, p. 191

11. Cummings BJ, Head E, Afagh AJ, Milgram NW, Cotman CW.Beta amyloid accumultaion correlates with cognitive dysfunction in the aged canine. Neurobiol Learn. Mem., 1996 Jul, 66:1 pp 11-23.

12. Cummings BJ, Head E, Ruehl W, et al. The canine as an animal model of human aging and dementia Neurobiol. Aging, Mar-Apr 1996, 17(2). pp. 259-68.

13. Hart BL, Hart LA, Selecting , raising and caring for dogs to avoid problem aggression. JAVMA, 210:1129-134; 1997

14. Chapman BL. Voith VL, Behavior problems in old dogs: 26 cases (1984-1987). JAVMA 196:944, 1990.

15. Landsberg, GM, The most common behavior problems in older dogs. Vet. Med 90: (suppl):16, 1995.

16. Landsberg, G. Diagnosing Cognitive Dysfunction Syndrome, Educational Publication Pfizer Animal Health, 1998.

17. Postal, JM, Effectiveness of Nicergoline in improving behavioural modifications associated with senility in dogs. Rhone Merieux Publication, France, pp.15-18.

18. Milgram, NW, Ivy, GO, Head, E, et al. The effect of L-Deprenyl on behavior, cognitive function and biogenic amines in the dog. Neurochemical Research, Vol. 18:12, 1993. Pp/ 1211-1219

19. Ruehl, WW, Entriken TL, Muggenburg BA et al Treatment with l-deprenyl prolongs life in elderly dogs. Life Sciences, 61(11), 1037, 1997.

20. Ruehl WW. Anipryl: hope for controlling canine cognitive dysfunction syndrome. In: Topics in Veterinary Medicine [special edition]. Pfizer Animal Health; 1999:8-12.

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Veterinary Technician/Office Staff Program
Don J. Harris, DVM
Heidi Hoefer, DVM, Diplomate ABVP
David Holt, BVSc, Dip. ACVS
Debra F. Horwitz, DVM, DACVB
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