Pet owners are able to take advantage of better preventive care, medical care and premium nutrition. The result is increased longevity and a larger population of elderly dogs. For owners, the bond with their pets grows stronger and more special the longer it lasts. This increases the importance of the geriatric pet’s health, quality of life and behavior. We need to help owners anticipate behavior changes associated with old age and provide help as problems arise. To accomplish this, good communication with our clients is very important. Although many owners recognize problems associated with old age in their dogs, most do not bring them to the attention of the family veterinarian. By asking pertinent questions during geriatric health exams and providing the necessary assistance, veterinarians can help preserve and strengthen the bond between the owner and pet.
Aging and Lifespan
We are learning more and more about the aging process in humans and animals. While the ultimate answers remain elusive, there are many theories. According to cumulative damage theories ionizing irradiation of genetic material or free radical damage to subcellular organelles underlies the aging process.1 Theories concentrating on waste product accumulation suggest that substances such as lipofuscin and advanced glycosylation compounds influence the aging process.1 The effects of immunologic events have also been suspected. It has been suggested that acquired cellular changes might result in antigenic stimuli and prolonged antigen-antibody reactions, or that decreased immune surveillance and the emergence of forbidden clones promote the aging process.1
We know that longevity is in part determined by genetic influences. Studies on human monozygotic twins support genetic influence in determining lifespan.1 It’s well known that small breeds of dogs outlive their larger counterparts. Environmental influences also play a roll. Medical care, nutrition, housing and stress are other important factors influencing longevity. Physical insults such as trauma, infection and toxins can all have a deleterious effect on lifespan.
Physical and Physiological Changes in the Older Dog
Older dogs have decreased total body water, decreased cell mass, an increase in body fat and a tendency towards obesity. They have decreased capacity to compensate for changes in acid-base balance and hydration . Renal function decreases along with a decease in the weight, number of nephrons, perfusion and concentrating ability of the kidneys. Cell-mediated and humoral immunity systems are less effective. A decline in respiratory and cardiac efficiency along with decreased cerebral blood vessel elasticity takes place.2 It’s possible that these changes may have a deleterious effect on cerebral O2 levels. In the oral cavity, gum recession, loss of alveolar bone and loss of teeth occur. Geriatric dogs have a decrease in gray and white matter volume in the central nervous system.3 This is accompanied by a deterioration of special senses, thickening of meninges and changes at the organelle and biochemical levels. Extremes in heat or cold are tolerated less well.
Changes in the senses are obvious in most geriatric dogs. Degeneration of peripheral acoustic structures such as cochlear ossicles, hair cells, ganglia and blood vessels, results in a decrease of high frequency hearing, as well as a general loss in hearing.4 The retina loses rods and cones and the and the lens tends to lose elasticity and clarity, resulting in loss of eyesight.2 Taste discrimination decreases along with the degeneration of taste papillae.1,25 The sense of smell lasts longest in dogs.
Older dogs are less active, show less interest in the environment and have diminished interest in food. They also have decreased alertness, exhibit less social interaction, are slower to obey, and learn more slowly.2 These changes likely reflect failing senses, decreased function and efficiency of the central nervous system, as well as decreased physical health and well being.
EFFECTS/CHANGES DUE TO AGING24 |
| METABOLIC EFFECTS OF AGING | BEHAVIORAL IMPLICATIONS |
| Decreased metabolic rate - increased obesity Thermoregulation capacity reduced Decreased immune competence Increase in autoimmune diseases Less sensitive to thirst - tissue dehydration Decreased ability to metabolize, or excrete drugs Increase in metabolic disorders affecting nervous system-hypothyroid, hypoglycemia (insulinoma), hepatic disorders, hyperlipidemia (Schnauzers) Decrease REM sleep, intermittent sleep | Decreased activity; obesity may affect locomotion, elimination, and other systems May affect any organ system Decreased tolerance of temperature changes, seeks warmth, avoids cold Constipation - stool housesoiling Caution with all forms of drug therapy! Pacing - seizures - restlessness - decreased mental alertness - geriatric onset behavior changes - Increased waking, appearance of restlessness |
| GASTROINTESTINAL |
| Increase in dental disease - can increase incidence of disease of other internal organs Decreased nutrient absorption
Decreased colonic motility Liver function decreases | Pain - Increased irritability - Aggression? Nutritional effects on behavior? - Changes in stool consistency leading to housesoiling? Hepatic encephalopathy & associated behavior |
| RESPIRATORY |
| Decreased respiratory capacity, reduced efficiency Decreased oxygen at the cellular level | Hypoxemia: Nocturnal confusion?, signs of senility? Decreased ability to do work |
| URINARY |
| Decreased renal function-decreased blood flow | Polyuria - decreased control. Housesoiling Behavior changes associated with uremia |
| Anemia due to erythropoietin decrease and uremia- hypertension - | CNS hypoxia? - confusion - restlessness |
| Prostatic hypertrophy | Pollakiuria/incontinence |
| Incontinence due to urethral incompetence, urinary tract infections and conditions leading to polyuria /polydypsia | Housesoiling due to decreased control or incontinence |
| ENDOCRINE |
| Decreased hormone production by thyroid, testis, ovary, and pituitary - may also be overproduction due to functional tumors (see below) | Decreased activity level - increased irritability or aggression - Decreased tolerance to cold |
| Testicular tumors (60% of older dogs): Sertoli cell-estrogen increase/androgen decrease Interstitial cell tumors - increased androgens | Medical/behavioral effects of increased estrogens Medical/behavioral effects of testosterone increase |
| Prostatic hypertrophy | Pollakiuria/Incontinence |
| Dysregulation of hypothalamic-pituitary-adrenal axis | Polyuria/ polydypsia/ panting/ polyphagia/ increased restlessness / housesoiling? |
| MUSCULOSKELETAL |
| Loss of bone and muscle mass | Weakness - decreased mobility - housesoiling? |
| Neuromuscular function deteriorates | Decreased mobility/activity - Incontinence - Housesoiling? |
| Cartilage degenerates/arthritis | Increased pain/irritability |
| CARDIOVASCULAR AND HEMATOLOGIC |
| Heart disease in 33% of dogs over 13 years old | Decreased exercise tolerance |
| Tissue and cellular anoxia leading to dysfunction or deterioration of other organs | Brain hypoxia leading to signs of senility? |
| Propensity toward anemia | Brain hypoxia - signs of senility? |
| NERVOUS SYSTEM |
| Increasing hypoxia due to anemia, cardiovascular disease, respiratory deterioration | Senility?, Cognitive decline? Effects on memory and previous learning |
| Tumor formation - primary or secondary | Cerebral: Abnormal sleep, change in eating, loss of housetraining, aggression, docility, visual deficits, circling, weakness Cerebellar: ataxia, tremor, head tilt, circling Brain stem: state of consciousness, cranial nerve deficits |
| Neurotransmitter changes: Increase in MAOB - decrease in dopamine Decrease in cholinergic system, decrease serotonin | Cognitive dysfunction, tremors?, pituitary dependent Cushing’s syndrome? Depression, sleep, and neuromuscular disorders |
| Cell numbers decrease: Neurons of the locus ceruleus and substantia nigra most affected Thickening of meninges | Reduced reaction to stimuli Irritable when disturbed, slow to obey commands, problems with orientation and learned behavior |
| Amyloidosis - Lipofuscinosis - gliosis - meningial fibrosis - Alzheimer like pathology | Cognitive decline? Senility? - Urinary incontinence, disorientation - alteration of sleep-wake cycles - geriatric onset behavioral problems Decreased performance in recognition/memory |
| SPECIAL SENSES |
|
| Decreased sight, smell, hearing | Hypersensitive to stimuli with less affected senses (e.g. sensitive to noise if blind) - Less responsive and alert to stimuli with affected senses Increased irritability? - Increased fear ? Changes in sleep-wake cycle - aggression - decreased appetite Increased vocalization |
Behavior Problems of the Geriatric Dog
Geriatric dogs exhibit many of the same behavior problems that we see in younger dogs. The major difference is that the senior age group has an increased incidence of cognitive and anxiety related disorders. Older dogs are more likely to have problems with thunderstorm phobias, separation anxiety, generalized anxiety disorders, panic attacks and cognitive dysfunction. It is likely that a number of the common behavior problems seen in older dogs result from degenerative, geriatric changes.5
Behavior problems may be primary problems or may occur as signs of underlying medical problems. Older pets have a relatively high frequency of medical problems and this makes the medical workup for a geriatric dog very important. This should include a thorough physical exam, neurological evaluation, serum chemistries, CBC, thyroid evaluation and urinalysis. Once medical problems have been taken into consideration and ruled out or corrected, attention may be given to treating the behavior problems. Therapy for many of the behavior problems exhibited by geriatric pets is basically the same as treatment of similar problems occurring in younger dogs. But there are some special considerations when working with geriatric patients. Learning and behavior modification may be slowed due to degenerative CNS changes. Pharmacologic choices may be narrowed due to underlying organic disease. There may also be some physical constraints on what the pet can be taught to do depending on its general state health.
Cognitive Dysfunction
Some dogs exhibit rather severe signs of mental deterioration as they grow older. These may include problems with recognizing familiar places or people, spatial disorientation and confusion. Loss of learned behaviors is common, a common sign of which is housesoiling. There may be problems with the sleep-wake cycle, inappropriate or excessive vocalization, and nonproductive, repetitive behaviors such as licking, circling or pacing. Signs of apathy, irritability, decreased awareness of the environment, and a reduction in social interaction with family members are common. In the absence of other disease processes, these changes are representative of cognitive dysfunction. This syndrome involves the loss of intellectual and integrative functions of the brain.19,23 In humans, severe cognitive dysfunction or dementia can result from cerebral hypoxia due to vascular disease or neurodegenerative lesions such as with Alzheimer’s disease.20 In dogs, hypothyroidism, chronic epilepsy, encephalitis, tumors and other structural diseases have been suggested to cause these types of severe behavior changes.3 Dogs with cognitive dysfunction appear to have underlying pathological CNS changes including amyloidosis, meningeal fibrosis and accumulation of ubiquitin-protein conjugates.21 These are some of the same changes seen in Alzheimer’s patients.21 Physiologically, these changes are thought to be associated with decreases in activity of the cholinergic or dopaminergic neurotransmitter system and increases in levels of monoamine oxidase.3
As the pet gets older, preventive measures such as providing a consistent, moderate amount of mental stimulation and exercise may help. Owners should review obedience commands and tricks with the pet as well as frequently engaging it in simple games of fetch, “find the biscuit,” round robin, etc. Treatment for cognitive dysfunction has traditionally been palliative involving changes in management, controlling the pet’s environment and nursing care. Anipryl® a (selegiline hydrochloride) is a selective monoamine oxidase-B inhibitor which shows great promise in alleviating signs of cognitive dysfunction in elderly dogs.22 While the exact mode of action of Anipryl® has not been demonstrated, suggested modalities include enhanced dopaminergic cell function, decreased dopamine catabolism by monoamine oxidase B inhibition, and reduction as well as increased removal of toxic free radical production. It also appears to be neuroprotective with apparent positive effects in decreasing programmed cell death of injured neurons and promotion of resynthesis of nerve growth factors.26
Miscellaneous Anxiety Disorders
There are some senior dogs that begin showing anxiety disorders of unknown origin. They may manifest signs of generalized anxiety or have actual panic attacks. Dogs with generalized anxiety problems may exhibit persistent, anxious vocalizing, trembling and hiding. They frequently seek the owner’s attention, act nervous and are easily startled. A variety of medical problems can contribute to this type of behavior, so a good medical work up is very important. With time the behaviors may also develop a conditioned component, since attention from the owner may serve as a reinforcement. Although the pathophysiology of these disorders is poorly understood at this time, there may be physiologic problems in the brain involving changes in neurotransmitter activity and receptor sensitivity.
A more intense manifestation of anxiety disorder in the older pet occurs in the form of panic attacks. Dogs with this condition may have acute episodes of intense anxiety involving severe panting, shaking and trembling. Rapid heart rate, respiratory rate and mydriasis are typically seen. The pet may suddenly run through the home in a frantic manner or seek a hiding area. The episodes usually occur in the evening or during the night. Psychomotor seizures may be an explanation for this behavior, or it may be an intense form of generalized anxiety disorder.
Treatment involves counseling the owner to avoid reinforcing the behaviors, increased physical and mental stimulation and medication. I have used benzodiazepines such as alprazolam and clorazepate successfully. Anipryl® might also be helpful since it has been used with reported success in Europe for anxiety problems such as separation anxiety. Phenobarbital may help the pet with panic attacks if the underlying problem is a seizure disorder.
Housesoiling Problems
The geriatric pet usually requires more frequent access to the outdoors. This may result from a decrease in bladder capacity due to obesity, reduced elasticity or prostatic enlargement. Medical problems seen in older pets that cause polyuria will increase the need to void more frequently. The frequency of defecation may increase when the overweight pet is changed to a diet that is high in fiber. If the owners are unable to change their schedule to accommodate the pet’s needs, a doggie door or paper training may be necessary.
Any problem that makes it difficult for the pet to get outdoors, such as weakness, muscular atrophy and arthritis, can lead to housesoiling. If it’s painful for the pet to get up or down stairs to eliminate, it may choose to avoid the discomfort and eliminate indoors. Medication to control pain, carpet runners on stairs for traction and control of obesity should help. Intolerance to adverse weather may also cause the pet to choose to eliminate indoors. This may be seen in hypothyroid patients during cold weather.
Treatment for housesoiling involves accompanying the pet outdoors as often as possible so that elimination in a desired location may be reinforced, consistent supervision/confinement, and a regular feeding schedule.7 Punishment should be avoided since it will likely make the problem worse or create other problems, such as social avoidance or fear aggression. However, it must be discussed with owners since harsh or delayed punishment is often used in an attempt to correct housesoiling.8 A sharp noise given during the act to interrupt the behavior is the only interactive correction that is acceptable.
Social Problems with Other Dogs in the Home
There are two types of social problems that might occur as the dog ages. The first occurs with the addition of a puppy to the home, and the second involves hierarchy problems with other adult dogs in the home.
Young puppies are full of energy and engage in assertive play involving chasing, attacking and biting. If the older dog is strong enough and has had adequate intracanine socialization, it will usually control the exuberant pup with threats and inhibited bites. If the pet is weak, passive or fearful it may withdraw and hide. Some dogs will become exceptionally anxious about having an active, young pup in the home. This may lead to housesoiling, excessive vocalizing, destructive problems and anorexia. If an older dog appears to be overwhelmed by a young puppy, the two should be separated whenever the owner is not around to supervise. Before allowing the pup and older dog to interact, the owner should provide enough exercise or play to fatigue the puppy. This will help ensure desirable interactions. All gentle play should be rewarded. The noise of a squeak toy may help distract the pup from engaging in play attacks. A long lead on the pup can be used for control and to apply a light correction. Attaching a head halter, such as the Gentle Leader® b will give the owner even more control. Occasionally, a timely squirt from a water gun or a toy tossed near the puppy will prevent or stop rough play.
Problems between adult dogs can occur between dogs who have lived together for years when the older, dominant dog becomes weaker and less assertive. The older dog may be challenged by a younger, confident dog in competitive or social situations. Problem situations may include soliciting attention from the owner, greeting visitors, exhibiting territorial displays, and guarding food or toys. The owners may make the situation worse by trying to protect and maintain the older pet’s dominant position. Theoretically, the owner might consider supporting a dominant roll for the younger pet by allowing it to have what it wants such as receiving treats and attention first from the owner, giving it access to desired sleeping areas, etc. But, in reality, it is very difficult for most owners to force the older dog to defer to a younger pet who has been a member of the family for a shorter period of time. A better solution is for the owners to reaffirm the family’s dominant roll in respect to both dogs. Obedience commands should be taught or reviewed. Both dogs should then be taught that the owners have complete control over anything that the pets desire. The owner can do this by requiring a response to a command before either pet receives anything (food, treats, play, a walk outdoors, and, especially, social attention). Whenever the dogs start to approach the owner, a guest, doorway, food bowl, etc., they should both be commanded to stay and, then, released, one at a time. The order in which the pets are released or receive attention, should vary each time. Establishing a strong dominant roll for the owners tends to reduce aggressive tension between the pets. In some cases, muzzles or head halters may be necessary for control and safety.
Aggressive Behavior
Pain can lower the threshold for aggressive behavior, so all pets with aggression problems should be carefully screened for signs of pain. Look for signs of arthritis, dental disease and otitis. Sensory deficits can also contribute to aggressive behavior. Fearful pets usually learn to avoid interactions that make them nervous by simply moving away from people that approach. When the pet loses its hearing or sight, it is more likely to be startled and display defensive or fearful aggression. Avoidance is usually the best way to handle this type of problem. Visitors should always be advised about approaching the pet with sensory deficits. In some cases it may be prudent to simply confine the pet to a safe, quiet area when visitors are in the home.
Although, cerebral vascular disorders are frequently blamed for apparent sudden onset of aggression, they are quite rare in the dog. A good medical and behavioral workup will usually uncover more common etiologies such as pain-elicited aggression, fear aggression or dominance aggression. The importance of ruling out and treating painful problems cannot be stressed enough. Failure to treat these will likely prevent successful resolution of the aggression problem. The treatment for fear aggression involves desensitization and counterconditioning.9,10,11 The owners of dominant dogs need to establish a dominant role for themselves in respect to their pet. This involves obedience training, control of resources, counterconditioning and desensitization exercises.12,13,14
Environmental and Social Stress
The elderly pet has a more difficult time dealing with stress. Stressful situation have the potential for triggering anorexia, destructive behaviors, excessive vocalization, housesoiling, displacement behaviors and stereotypical behavior. Changes in the owner’s schedule or in the amount of time the owner spends with the pet can be very unsettling. In Chapman and Voith’s study of older dogs referred for behavior problems,6 separation anxiety was the most common cause of destructive behavior and excessive vocalization. The majority of dogs over ten years of age that I have seen for destructive behavior have had separation anxiety as the underlying etiology. Treatment for separation anxiety has been described15,16,17 and involves changing the way the owner interacts with the pet so that it is not always getting attention on demand, gradually accustoming the pet to absences by the owner and, in some cases, prescribing anxiolytic medication such as tricyclic antidepressants, benzodiazepines and selegiline. It is helpful to reward play with toys when the owner is present and to provide food-laced toys at departure.18 Taste-aversive sprays can be used on objects around the house to teach the pet to avoid them.
Long trips and boarding should probably be limited or carefully thought out. If major changes in the pet’s life are anticipated, some care should be taken to gradually introduce the pet to these. If sudden, major changes are unavoidable and the pet responds very anxiously, anxiolytic medication may be helpful.
