Ageing is an inevitable process and veterinary surgeons cannot offer any miracle solution to this problem, but with increasing knowledge about the ageing process and the ways in which it can be affected by diet, lifestyle and medication, they can offer the means of increasing the quality of life for the ageing pet population.
Canine cognitive dysfunction
Canine cognitive dysfunction is a medical condition but in most cases there is a lack of recognisable clinical symptoms and the signs that lead to accurate diagnosis are almost entirely behavioural. Without the appropriate line of questioning in the consulting room many of these cases will go undetected. There are four main categories of presenting signs for this condition namely disorientation, changes in social and environmental interaction, changes in sleep/wake cycle and breakdown in housetraining. On their own each of these categories could be indicative of organic disease or 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 canine cognitive dysfunction needs to be considered.
Asking the right questions
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 to include a behavioural questionnaire in routine geriatric clinics. Asking specific questions about the dog's social behaviour both at home and on walks, as well as seeking information about sleep patterns and toileting habits will enable the veterinary practice to spot cases early and institute treatment as quickly as possible.
In all of the categories of behavioural symptoms for canine cognitive dysfunction there are a number of medical differentials. Sensory deficits need to be considered when signs of disorientation, changes in social interaction and changes in sleep/wake cycles are encountered since a dog 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 investigated in cases where a break down in housetraining is the major presenting sign and metabolic diseases and endocrine disorders which result in polyuria and polydipsia will form part of the list of differential diagnoses. These clinical considerations highlight the need for a medical approach to these cases and a combination of clinical examination and additional tests, such as blood samples, will enable the veterinary surgeon to determine the dog's physical state of health. Only once this has been done can the behavioural investigation continue and treatment for canine cognitive dysfunction be considered.
Medication for canine cognitive dysfunction
Although primarily behavioural in presentation there can be no doubt that canine 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 a compromising of the cerebral blood flow and medication with the appropriate drugs, such as nicergoline and propentofylline, can vastly improve this situation and give increased energy and vigour to dogs that are beginning to slow down. In addition these drugs improve cerebral metabolism through neuroprotective functions and one of the main functions of propentofylline is as a glial cell modifier as well as increasing levels of adenosine. In cases of canine cognitive dysfunction additional 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 order to deal with these changes administration of the drug selegiline hydrochloride is recommended. Selegiline has three important actions in cases of canine dementia. It enhances brain dopamine concentrations and metabolism, it decreases substances in the brain, which are responsible for neural cell damage, and it protects nerve cells, decreases cell death, and promotes synthesis of nerve growth factors. It is administered as a once daily dose at a rate of 0.5 mg/kg and in cases of dementia the dog will usually require long term medication. It can take up to six weeks for selegiline to take effect when treating emotional disorders in dogs but in cognitive dysfunction cases improvement is often noted by the owner within 3 weeks. It is recommended that all dogs are given pre-treatment biochemistry and haematology screens and that these blood profiles are repeated at six monthly intervals during treatment. Side effects are minimal but some owners do report transient self correcting episodes of vomiting and diarrhoea during the first week of treatment. 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 with selegiline and propentofylline.
A nutritional approach to canine cognitive dysfunction
It has long been accepted that nutrition can play a vital role in the treatment of systemic disease and in cases where behavioural problems in the geriatric pet are attributable to organic disease, 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, such as "Hills b/d"®, or nutritional supplements, such as "Aktivait"®, 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 canine cognitive dysfunction is currently the subject of extensive research and it is likely that further developments will be seen in the near future.
Providing behavioural support for a medical condition
Although canine 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 the dog may lose its ability to perform simple tasks or respond to previously known commands. Teaching dogs with cognitive dysfunction needs patience and understanding and 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 house trained and in many cases owners also need to reintroduce some of the basic obedience commands. It is important that the owner begin this re-training as early as possible in order to avoid the establishment of unsuitable behaviours through inappropriate learning.
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 the owner should be encouraged 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, 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 effect of treating canine cognitive dysfunction on the pet-owner relationship
The onset of old age is an inevitable fact of life and for many dogs 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 these dogs to receive appropriate veterinary care and maximise the benefits of therapy in terms of increased quality and duration of life. Practices can vastly improve their service to geriatrics by incorporating a programme for the early detection of canine cognitive dysfunction into their geriatric clinics.
1. Bain M J, Hart B L, Cliff K D and Rheul WW (2001) Predicting behavioral changes associated with age related cognitive impairment in dogs JAVMA 218 1792-1795
2. Chapman B L and Voith V L (1990) Behavioral problems in old dogs 26 cases (1984-1987) J Am Vet Med Assoc 196: 944-946
3. Cummings B.J, Su J, Cotman C , White R, Russel M (1993) Beta amyloid accumulation in aged canine brain: A model of early plaques formation in Alzheimer's disease. Neurobiology of Ageing 14: 547-560
4. Cummings B.J., Head E., Afagh, A.J., Milgram N.W., Cotman C.W. (1996a) Beta Amyloid accumulation correlates with cognitive dysfunction in the aged canine. Neurobiology of Learning and Memory 66: 11-23
5. Cummings B.J., Head E., Ruehl, W., Milgram N,W., Cotman C.W., (1996b) The canine as an animal model of human aging and dementia. Neurobiology of Ageing, 17: 259-268
6. Head E 2001 Brain aging in dogs: Parallels with human brain aging and Alzheimer's disease Vet Ther 2 (3) 247-260
7. Houpt K A and Beaver B 1981 Behavioral problems of geriatric dogs and cats Vet Clinics of North America Small Animal Practice 11: 643-652
8. Kitani K, Kanai S, Ivy G O, Carrillo M C 1998 Assessing the effects of deprenyl on longevity and antioxidant defences in different animal models Ann NY Acad Sci 854; 291-306
9. Lim G P, Yang F, Chu T et al (2000) Ibuprofen suppresses plaque pathology and inflammation in a mouse model for Alzheimer's disease J Neuroscience 20: 5709-5714
10. Milgram N W, Head E, Weiner E, Thomas E 1994 Cognitive functions and aging in dogs: Acquisition of nonspatial visual tasks Behav Neurosci 108; 57-68
11. Milgram N W, Estrada J, Ikeda-Douglas C et al 2000 Landmark discrimination learning in aged dogs is improved by treatment with an antioxidant enriched diet. Abstr. Soc. Neurosci 193: 9
12. Milgam N W, Head E, Cotman C W, Muggenburg B, Zicker S C (2001) Age dependent cognitive dysfunction in canines: Dietary intervention in Proceedings of the 3 rd International Congress on Veterinary Behavioural Medicine Ed Overall K L, Mills D S Heath S E, Horwitz D UFAW Wheat Hampstead England pp 53-57
13. Mills D S 2000 The ageing mind and its pharmacological support CABTSG Newsletter Volume 20
14. Morris J C 1996 Diagnosis of Alzheimer's disease In Alzheimer's disease: cause(s), diagnosis, treatment and care Ed Khachaturian Z S and Radebuagh T S Boca Raton FL: CRC Press pp 76-81
15. Penalligon J., 1997 The use of nicergoline in the reversal of behaviour changes due to ageing in dogs: a multi-centre clinical field. In: Proceedings of the 1st International Conference on Veterinary Behavioural Medicine. Ed Mills D.S., Heath S.E, Harrington L.J. UFAW, Potters Bar pp 37-41
16. Ruehl W W, DePaoli A and Bruyetter D (1994) Pretreatment characterization of behavioral and cognitive problems in elderly dogs J Vet Int Med 8:178
17. Ruehl W W and Hart B L (1998) Canine cognitive dysfunction In Psychopharmacology of Animal Behavior Disorders Eds Dodman N H and Shuster L Blackwell Science Publication Malden USA pp 283-304
18. Sieffge D and Katsuoshi N., 1985 Effects of propentofylline on the micromechanical properties of red blood cells. Drug Development Research 5: 147-155