Sarah Heath
As the state of health care continues to improve more and more of the human population are living long enough to have to deal with the varied implications of old age and society is recognising that the ageing population has specific needs. In a similar way the pet population is steadily growing older and the proportion of pets that qualify as geriatrics is increasing. With this change in population comes a need to recognise the specific requirements of this special group of animals, in terms of their behavioural and emotional needs, and to offer appropriate support for their owners.
Ageing is one of those inescapable facts of life and veterinary surgeons are no more able than their medical counterparts to offer any miracle solution to the issue of old age. However, there is now a considerable body of information available about the changes that occur during the ageing process and about how these changes can be affected by diet, lifestyle and medication. With this knowledge at our finger tips we can certainly increase the quality of life for the ageing pet population and ensure that pets and their owners get the most from their relationship at this time.
Advances in veterinary medicine over recent years have meant that old pets are now offered the very best in medical care during the later years of life and many will enjoy excellent physical health into their late teens and even beyond. However it is also important to remember that ageing affects not only the major organs such as the heart, lungs, liver and kidneys but also the nervous system and more specifically the brain. Changes in neurotransmitter levels, alterations in membrane permeability and increased production of free radicals within the central nervous system can all lead to the onset of age related behavioural changes and when pets begin to show symptoms related to these changes they begin to require a very specific form of veterinary attention. Of course behavioural changes in elderly patients are not always related to specific issues of brain ageing and the potential involvement of medical conditions such as pain, failing sensory systems, compromised blood flow to the central nervous system and age related deterioration in functioning of the major organs, such as liver, kidneys and heart, all need to be considered. In addition environmental and psychological factors should not be overlooked and it is important to remember that older animals may be less adaptable to change in their social or physical surroundings and may show marked behavioural changes in response to changes in their household or routine as a result.
As the ageing process takes its toll on a dog’s heart and brain some changes in behaviour and personality are almost inevitable and it is important to be able to differentiate between cases where the animal is simply slowing down and those where the animal is finding it increasingly hard to function at a social level. In some cases behavioural changes in old dogs will noticeably resemble the symptoms of senility or Alzheimer’s disease in people. Lack of connection between behaviour and context is a classic sign of brain ageing and many owners have reported that their pet seems like a stranger in its own home. In cases of cognitive dysfunction in dogs and cats post mortems have shown similar neuropathological lesions to those seen in people with Alzheimer’s disease and there is no doubt that this condition is part of mainstream veterinary medicine.
Cognitive dysfunction is the name given to the age related progressive neurodegenerative disorder which is characterised by specific behavioural changes, and physical modifications of the central nervous system, such as the deposition of beta amyloid plaques, production of free radicals and onset of vascular changes, which lead to characteristic neuropathololgy.
Unlike its physical counterparts cognitive dysfunction is characterised by a lack of recognisable clinical symptoms and this can lead to difficulty in identifying cases, especially in the early stages of the condition. Patients suffering from CD primarily exhibit changes in their behaviour and unless owners are asked the right sorts of questions it is easy for the disease to go undetected. Alterations in learning and memory together with changes in social interaction, sleep wake cycles and activity patterns are traditionally associated with the condition and specific changes in the perception of and response to stimuli in the environment, in levels of anxiety and restlessness and in spatial orientation and levels of confusion are also identified.
In order to assist in the clinical evaluation of these cases the behavioural changes associated with this condition are commonly divided into four main groups, namely:
• disorientation
• changes in social and environmental interaction
• changes in sleep/wake cycle
• changes in response to learned associations and commands.
On their own each of these categories could be indicative of a physical disease or could be the result of a purely behavioural condition but when signs are present from each of these categories, and most importantly from the first two, a diagnosis of cognitive dysfunction needs to be considered.
A study by Neilson and colleagues in 2001 showed that 28% of dogs in a population aged between 11 and 12 years and 68% of a population aged between 15 and 16 years showed at least one sign which was consistent with a diagnosis of canine cognitive dysfunction and yet only 12 % of pet owners reported these changes to their veterinary practice. One of the reasons for this discrepancy may be that many owners are reluctant to speak to their veterinary practice for fear of being advised to consider euthanasia for their beloved companion. As a result they tolerate changes in their pet’s behaviour, seeing them as an inevitable effect of growing old, rather than a symptom of a underlying disease process that can be managed, even if it cannot be cured, and the belief that nothing can be done to change them will drive many owners to make considerable changes in their own lifestyle in order to accommodate their pet’s peculiar ways.
Alterations in sleep/wake cycles can take the largest toll on the humans in the household but owners will often put up with broken nights and significant sleep deprivation rather than approach their veterinary practice and run the risk of being persuaded to put their pet to sleep. Break down in housetraining can also put an enormous strain on the pet owner relationship but many owners feel guilty about their negative feelings toward their pet and chastise themselves for not being patient with their ageing companion at these difficult times. After all quality of life is a difficult concept and it is important to remember that the criteria by which owners judge the quality of their pet’s life will be very different from those that a detached professional might employ. The pet is a valued member of the owner’s family and its behaviour is often one of the major indicators of the strength of that relationship as well as one of the most significant sources of strain upon it. However, in the context of old age forgiveness for changes in sleep patterns and breakdowns in housetraining is usually forthcoming from owners who see these as an inconvenience that simply has to be endured.
In contrast changes in social interaction and signs of disorientation are not seen as inconvenient alterations that need to be accommodated, but rather as indicators of the pet’s distress. Owners find it upsetting to see their companion looking confused and when their dog fails to respond to previously known commands or their cat startles when they enter the room as if he does not recognise them the effect on the pet-owner relationship can be devastating. Feelings of guilt at the prospect of prolonging life for a pet that is no longer fully aware of its surroundings can be very real but belief that euthanasia is an unacceptable way out can lead to emotional conflict that owners find hard to resolve. Some find it hard to forgive themselves for even considering euthanasia when their pet appears to be in such good physical health, since human society frowns upon the concept of euthanasia and the only way of justifying it in a veterinary context is as a means of stopping physical suffering. Putting to sleep due to changes in behaviour is therefore seen by many owners as a convenience and this only adds to the guilt.
Although most of the companion animal literature relating to behavioural changes in old age have been concerned with the dog, some work on the effects of ageing on feline behaviour has also been carried out. In a prevalence study conducted by Landsberg and colleagues in Canada 35% of cats over 11 years of age demonstrated signs of cognitive dysfunction, which were not complicated by any other medical condition, and 30% of cats between 11 and 15 years were affected. In the category of cats older than 15 years the percentage of affected cats increased to 48% and these cats also showed more signs of the condition than their younger counterparts.
The presentation of cognitive dysfunction in a feline context is very similar to the condition in dogs and to related conditions in people, with signs of confusion, disorientation, alteration in social behaviour and breakdowns in house training all being reported. Night time waking, excessive vocalisation and aimless wandering and pacing are also commonly cited in the ageing feline population and changes in sleep/wake cycles appear to be the most commonly reported change in the population of cats older than 15 years.
Noticing the signs of cognitive dysfunction early on is crucial and there is a much better prognosis in terms of the level of improvement and the extension of good quality life if treatment is instituted in the early stages of this disease. However, it is this early stage that often goes unnoticed and the most effective way of increasing the detection rate for this condition is for elderly pets to have regular veterinary examinations, which include a behavioural a well as a physical health check. Information about the animal’s social behaviour, as well its sleep patterns and toileting habits, will lead to early detection of the condition and allow treatment to be instituted as quickly as possible.
In order to assist in the early detection of cognitive dysfunction in dogs it can be useful to divide the areas of investigation into the four main categories and then to ask questions which are designed to identify alterations in behaviour. A similar approach will be needed in the investigation of feline cognitive dysfunction but at present far more is known about the subtle signs seen in dogs and information about treatment opportunities is certainly more readily available in the canine field.
Dogs suffering from cognitive dysfunction will show a delay in the recognition of people, places and objects and in some cases there may be no recognition at all. Obviously when dogs fail to recognise their owners this is likely to be noticed quite quickly, but failure to respond to people who call regularly at the house or to those that are met while out on daily exercise may go unnoticed for quite some time. The way in which the dog greets people at home and on walks can help to identify canine cognitive dysfunction in its early stages. Some old dogs suffering from cognitive dysfunction will wander aimlessly around the house and it may be obvious that these individuals are disorientated and confused but in other cases more subtle alterations in the dog’s reaction to previously familiar objects, such as household furniture and trees and bushes in the garden, can help to pinpoint the symptoms of cognitive dysfunction. These dogs will often bark at these objects as if they have never been seen before and some may show real fear. Failure to recognise the home driveway on the return from a walk or a tendency to sit at internal doors when asking to go out into the garden can also be symptoms of disorientation and unexplained staring is another potential indicator of this condition.
One of the most obvious signs of a lack of connection between context and behaviour is seen in the interactions that older dogs have with the people and other dogs that they come into contact with. One of the most distressing examples of this is an alteration in the social interaction between the dog and its owners and a decrease in the enthusiasm of greeting behaviour. Together with a decrease in the time spent engaging in play and in affectionate interaction this can signal the onset of age related brain changes. There is often a change in the consistency and speed with which these dogs respond to commands and owners often mistake this change for stubborn behaviour. When considering interactions with other dogs it is not uncommon to see an increase in confrontational reactions in other dogs that appear to be threatened by the bizarre behaviour of the geriatric individual. Dogs suffering from cognitive dysfunction may also become more irritable themselves and owners may be aware of an increase in aggression from their dog together with a general decrease in the desire to interact and play with other dogs on walks.
Alterations in sleep/wake cycles are common in cases of canine cognitive dysfunction but unless the dog is disrupting the owner’s sleep this aspect may easily go unnoticed. When the dog is whining or barking at night most owners will rapidly respond by taking their pet out into the garden on the assumption that it needs to relieve itself but dogs suffering from cognitive dysfunction will rarely need to eliminate on these occasions. In some cases they may respond to being outside by toileting but once back in the house they will be very slow to settle and will soon recommence barking and whining. Pacing is another common feature in these cases and owners often comment that their dog shows signs of agitation and restlessness at their usual bedtime and paces and vocalises when they make preparations to go to bed. Waking in the middle of the night is another classic symptom of cognitive dysfunction and since these dogs are also disorientated and confused they will often seek out their owners when they wake. If the dog is housed downstairs during the night this may cause the dog to scratch at doors and this symptom can commonly lead to confusion with separation anxiety. During the day the sleep/wake cycle is also affected and dogs suffering from the behavioural effects of brain ageing will sleep for longer in the day but once again this symptom may easily be overlooked and considered to be a normal change in a dog of advancing years.
Break down in house training is probably the most documented example of this change in behaviour and can occur in cases of canine cognitive dysfunction for two reasons. Firstly the disorientation associated with the condition can lead to a situation where dogs sit at internal doors when they want to go out into the garden and owners can easily disregard this signal until it is too late. Staring at the hinged side of the door rather than the handle side has also been noted by owners and in these cases they often observe the peculiar behaviour but do not recognise it as a signal for needing access to outdoors. Another factor in the house training problems associated with old age behavioural changes is a failure to maintain associations with suitable latrine substrates and in many cases there is a history of a progressive break down in associations leading to elimination in a wide range of unsuitable locations. These dogs often start by not always toileting on grass as they have done in the past and making mistakes on the patio, on the flowerbeds and eventually on the carpeted floors in the house. In many cases the onset of this problem behaviour is gradual and it is only when the dog is toileting in a number of locations that the owners realise that these are not one-off accidents.
In all of the categories of behavioural symptoms for cognitive dysfunction there are a number of medical conditions that need to be considered as potential causes. Deterioration in sensory functions, such as sight and hearing, need to be considered when signs of disorientation, changes in social interaction and changes in sleep/wake cycles are encountered, since an animal that is not fully aware of its surrounding through a lack of sensory input can easily present with signs which resemble those seen in cognitive dysfunction. Cardiovascular and neurological disorders will also need to be ruled out and the influence of pain on activity levels, social interaction and sleep patterns should be investigated. Disorders of the gastrointestinal and urinary tracts will need to be considered in cases where a break down in house training is the major presenting sign and medical conditions which result in increased thirst or increased urination will also need to be included in the investigation. Only once a thorough medical investigation has been carried out by a veterinary surgeon can the behavioural investigation continue and treatment for cognitive dysfunction be considered.
Most of the proactive research into the treatment of cognitive dysfunction has been carried out in dogs and at the moment medications and specifically formulated diets are only marketed for dogs suffering from this condition. However, recent work in Canada has suggested that a similar therapeutic approach consisting of a combination of dietary management, medical treatment and behavioural therapy is just as applicable to the feline population.
Although primarily behavioural in presentation there can be no doubt that cognitive dysfunction is a medical condition and when deciding on medication to treat these cases it is important to consider the changes that are occurring within the body systems including the central nervous system. During the normal ageing process behavioural changes can result from changes in the blood flow to the brain and medication with drugs which enhance the availability of good cerebral circulation can vastly improve this situation and give increased energy and vigour to dogs that are beginning to slow down. In addition there are drugs which lead to a protective effect on the central nervous system and these may be beneficial in cases of canine cognitive dysfunction where internal changes such as a depletion of brain dopamine levels and an increase in the presence of free radicals, leading to cell injury and brain pathology, need to be considered.
In the United Kingdom and the USA there has been a lot of publicity relating to the use of selegiline hydrochloride as a therapeutic approach to cognitive dysfunction and three important actions have been identified in relation to the treatment of these cases. Firstly selegiline enhances brain dopamine concentrations and metabolism, secondly it decreases substances in the brain, which are responsible for neural cell damage, and thirdly it protects nerve cells, decreases cell death, and promotes synthesis of nerve growth factors. It is administered as a once daily dose and in cases of dementia the dog will usually require long term medication. The onset of action of the drug is not immediate and it has been reported that clinical changes have been delayed for up to six weeks after commencing treatment. However others report changes within three weeks. In long standing cases of canine cognitive decline it has been reported that the effects of single drug therapy may not be sustained and that such cases may respond better to combination therapy but in such situations it is important to discuss the dog’s behaviour in detail with a veterinary surgeon who can monitor responses to treatment and modify treatment as appropriate.
It has long been accepted that nutrition can play a vital role in the treatment of organic disease and in cases where behavioural problems in the geriatric pet are attributable to conditions such as renal failure, the use of prescription diets should obviously be considered. However, recently there has been increasing interest in the role of nutrition in the treatment of age related progressive degeneration of the central nervous system and in the clinical consequences of that process. In particular research has looked at the effects of dietary manipulation on canine short-term memory and has assessed this with reference to particular learning and memory tasks. This is particularly significant in relation to treatment of canine cognitive dysfunction since loss of short term memory is known to be one of the first indications of similar conditions in humans. Researchers have found that cognitive performance can be improved with a diet supplemented with a broad spectrum of antioxidants, which are believed to prevent the development of the age-related neuropathology. In addition antioxidants are believed to promote recovery in neurons that are exhibiting signs of neuropathology and therefore commercially available diets and nutritional supplements, which are enhanced with these agents, are believed to offer another option in the treatment of behavioural disorders in the older pet. The role of nutrition in the prevention and treatment of both canine and feline cognitive dysfunction is currently the subject of extensive research and it is likely that further developments will be seen in the near future.
Although cognitive dysfunction is undoubtedly a medical condition there is a strong behavioural component and behavioural therapy is needed as a support for the pharmacological treatment. One of the consequences of age-related behavioural disorders is the loss of learned responses. As a result dogs may lose the ability to perform simple tasks or respond to previously known commands and cats may show a breakdown in house training or a reluctance to respond to being called in from the garden. Obviously re-establishing these learned responses is particularly relevant in treating cases of canine cognitive dysfunction and teaching these dogs old tricks will involve a large amount of patience and understanding. The use of simple unambiguous commands and clear reward signals is essential. Ideally rewards should be things that the pet particularly values and this will be dependent on the breed and will also vary from individual to individual. For example some dogs will value games, others petting and others food. The use of a clicker, which has been previously associated with reward in a simple introduction process, gives the pet a clear unambiguous signal that will help to reinforce success. Patients will often need to be taught commands from scratch and house training and introduction of very basic obedience commands will be part of the process. The aim of behavioural therapy in these cases is to give structure and predictability to the environment in a way which helps the dog to understand what is expected. Cognitive dysfunction results in a lack of association between action and context and therefore it is important to ensure that all commands are consistent and that the dog is given as many clear signals of success as possible. Visual signals can be very useful, provided the dog is not showing any sensory deficits of course, and marking exit doors can be beneficial for those dogs showing signs of disorientation leading to house soiling problems.
Cognitive dysfunction patients often show difficulty in concentrating and therefore it is important to introduce games that will provide mental stimulation and increase social interaction with their pet. Ideally play and exercise sessions should be of short duration and involve simple tasks, which are repeated frequently and culminate in a positive reward for the pet. For example, several short exercise outings each day will be preferable to one long one since this will stimulate the pet’s interest in the environment and provide increased opportunities for interaction between the pet and its owner.
The onset of old age is an inevitable fact of life and for many pets their transition into the ranks of the geriatrics is smooth. However this is not always the case and when signs of disorientation and confusion begin many owners find it hard to recognise their faithful family friend. The changes in social interaction can make brain ageing a distressing condition for the owner and when dealing with these cases it is important to remember the human element. Detecting the symptoms of this condition at the earliest opportunity will enable pets to receive appropriate veterinary care and maximise the benefits of therapy in terms of increased quality and duration of life.