Cognitive dysfunction is a progressive neurodegenerative disorder thought to be due to compromised cerebral blood flow, chronic free radical damage and amyloid deposition (Gunn-Moore et al, 2007). The term “cognition” covers a range of mental processes including perception, awareness, learning, memory and decision making, which together govern an animal's response in a given situation (Shettleworth, 2001).
Heiblum et al (2007) suggest an increase in geriatric population may allow time for cognitive dysfunction to be better observed and understood. Cats and dogs like humans are now living healthier, enriched and longer lives (American Association of Feline Practitioners, 2005) (Figures 1 and 2). The UK is estimated to have 2.5 million senior cats (11–14 years), approximately 30% of the pet cat population (Gunn-Moore, 2010). Cognitive dysfunction affects 14.2% of older dogs over 8 years of age (Salvin et al, 2010). In cats 28% of those aged 11 to 14 years develop one geriatric-onset behaviour problem (Gunn-Moore, 2010). This increases to over 50% in cats 15 years of age and older. Welfare and quality of life is a significant issue for these older animals (Landsberg et al, 2011).
Moffat and Landsberg (2003) suggest veterinary clinics need to have a proactive approach supporting owners to recognise and report behaviour signs for diagnostic evaluation (Landsberg et al, 2010). Lack of identification of this common condition by veterinary surgeons (VS), with only 1.9% of dogs being identified is disturbing (Salvin et al, 2010). Owners do not report clinical signs as they see these as a normal part of ageing (Head et al, 2008). It is of paramount importance therefore that cognitive dysfunction is recognised, and if possible treated with support given to owners to ensure better quality of life for their pets.
Cognitive dysfunction presents with age-related behavioural signs, independent of a medical or behavioural diagnosis with similar features to early human Alzheimer's disease (Landsberg et al, 2011).
Cognitive dysfunction in dogs
Head (2013) suggests while dogs do have natural cognitive decline in different domains, like humans this is individual to the animal. Clinical behavioural signs are often referred to by the acronym ‘DISHA’ (Landsberg et al, 2010), and are defined as: disorientation; interactions; sleep:wake cycle; house soiling and activity, these are listed in Table 1. Other signs can include increased anxiety. When accompanied by other ageing issues such as impaired senses and physical disabilities, aggression can manifest (Bowen and Heath, 2005). This can lead to deterioration in the human–animal bond due to unwanted behaviours and can result in welfare and quality of life issues (Bennett, 2012).
| Cats | Dogs |
|---|---|
| Altered behaviour including altered interactions with the family | Disorientation |
| Spatial or temporal disorientation | Altered interaction with owners, other pets and the environment |
| Inappropriate elimination; changes in activity including sleep/wake cycles; and/or | Sleep:wake cycle disturbances |
| Inappropriate vocalisation | House soiling and activity alterations |
Progression of the condition can be slowed down by behavioural and environmental adjustment in conjunction with medical therapy (Crowell-Davis, 2008).
Different cognitive tests developed for canine memory and learning are not always practical for use in veterinary practice because of the time and training required of the person carrying out the test (Frank, 2002). Dogs with cognitive dysfunction demonstrated reduced or less intense interactions and recognition of family members, a tendency to get lost in familiar places in the home and inappropriate elimination with whining, wandering and wakefulness at night. Dogs presenting with these signs require a complete physical and neurological examination and blood and urine profile to exclude any medical/surgical condition. Cognitive dysfunction however may occur concurrently with such conditions.
Cognitive dysfunction in cats
While canine cognitive decline may be seen from 7 to 8 years of age, in cats 15 years and older 50% have pathological signs of cognitive dysfunction (Head et al, 2005). Recent research into cognitive dysfunction in cats is based on neuropathological, cognitive and behavioural evidence (Landsberg et al, 2010). However few tests prior to a T-maze, a boxed maze which aims to test cognitive and motor ability (Figure 3), have developed to measure cognitive and motor capabilities in domestic cats (Sherman et al, 2013).
Initially it was uncertain as to whether cats developed cognitive dysfunction, however, Landsberg et al (2010) describe similar behaviour signs to dogs occurring in older cats with excessive vocalisation being a key sign (Moffat and Landsberg, 2003) (Table 1).
Pittari et al (2009) state feline treatments are extrapolated from studies in humans and dogs. As with dogs, it is essential to rule out medical problems in the first instance. The older the cat the increased rate of behavioural changes (Gunn-Moore et al, 2007). Interestingly alteration in social interactions with people and other pets appears earlier than behavioural alterations such as aimless activity and excess vocalisation. This may indicate a particular sign to screen for when first assessing for cognitive dysfunction in older cats.
Treatments for cats include diet enrichment, environmental management and medication. Diet enrichment with antioxidants and other compounds such as vitamin C and E, fruit and vegetables, used in dog and human studies, are thought to reduce oxidative damage and amyloid production and improve cognitive dysfunction (Milgram et al, 2004). However not all dietary modification effective for dogs can be used for cats (for example alpha lipoic acid is toxic to cats (Gunn-Moore, 2010)). Environmental management can improve quality of life but it is important to understand that cats with cognitive dysfunction are very easily stressed especially in relation to elimination and litter box concerns (Pittari et al, 2009). Indeed any environmental changes can have a negative effect with increased signs of cognitive dysfunction (Gunn-Moore, 2010). However, minimal slow change with reassurance and possibly confinement of the cat to a single room where all its needs can be met, is beneficial (Pittari et al, 2009; Gunn-Moore, 2010).
There is no licensed medication for cats (Landsberg, 2006), however selegiline has been used with some success in dogs and cats (Landsberg and Araujo, 2005).
What research is there that can inform practice?
There are numerous studies on areas of cognitive dysfunction in cats and dogs which the veterinary nurse (VN) can influence. Older companion animals often do not get focused support in practice, as puppies and kittens do, in relation to behaviour, particularly of learning ability and memory. These animals, which have often given many years of pleasure and formed a close human–animal bond with their owner, deserve similar emphasis on their physical and mental well-being. Detection of the behavioural signs of cognitive dysfunction and discussion with owners about diets, behaviour and environmental enrichment (Bevan, 2009), in liaison with the VS, can form the basis of well-managed older pet clinics. This can often transform quality of life for these animals. VNs are well equipped to carry out these clinics allowing informed discussions with owners to support and promote the welfare and quality of life of older pets.
What does the literature show?
There is significantly more primary research on cognitive dysfunction in dogs than cats. The reason appears to be studies, certainly for treatments, are extrapolated from dogs and humans.
Studies have focused on either behavioural or clinical signs related to cognitive dysfunction, cognition tests to measure behavioural responses and nutritional studies (nutraceutical supplement and/or specified diet) which support identification of cognitive dysfunction particularly in dogs in the clinical setting, and suffices to support not only identification of the condition but also successful interventions. It is important however to remember both in the research of and management of any condition quality of life and prevention of pain or distress must take precedence (Rollin, 2007).
How to put the research into practice
While there is significantly greater research of cognitive dysfunction in dogs than cats, there is sufficient to support identification of behavioural manifestations in both species.
Progression of canine cognitive dysfunction can be delayed with diet, behaviour and pharmalogical treatment (Landsberg and Araujo, 2005; Studzinski et al, 2006; Heath et al, 2007, Azkona et al, 2009). Early diagnosis is therefore crucial.
Females are significantly more affected and have twice the chance of developing age-related cognitive impairment, and neutered dogs' prevalence and odds are significantly higher than those that are not neutered (Azkona et al, 2009). However, focus should be given to all older pets irrespective of size, breed and neuter status, but it should be understood that larger breeds ‘age’ sooner than smaller breeds (Heath et al, 2007). Reduced social interaction and loss of house training was identified by Azkona et al (2009) as significant in dogs that were mostly impaired. Therefore these behaviours need to be measured in any proposed screening tool for older dogs. Age-related behavioural impairment is frequently underestimated as owners often believe that these problems are due to age and untreatable.
The behaviours of all older pets irrespective of size, breed and neuter status should be measured using a screening tool which includes asking about reduced social interaction and loss of house training. This information can be used by VNs to educate clients. The use of suitable behaviour tools (Landsberg and Araujo, 2005) during older pet clinic checks will aid early identification. While Salvin et al (2010) identified a 13 item scale with 99.3% diagnostic accuracy for canine cognitive dysfunction, a less complex tool able to identify pre-canine cognitive dysfunction state would support early pharmaceutical, nutraceutical and behavioural and environmental management. Fast et al (2013) identified four clinical signs which would be of use in practice (Table 2).
| Sleeping during the day and restless at night | Disorientation at home |
| Decreased interaction | Anxiety |
In particular dogs with pre-canine cognitive dysfunction status had an increase in day-time sleeping (Salvin et al, 2010; Landsberg et al, 2012). While several of the other studies used cognitive tests which may not be practical in an every-day clinical setting within the veterinary practice some simple checks can be used effectively without extensive training by the VN. Salvin et al (2011) and Gonzalez-Martinez et al (2013) identified that dogs with canine cognitive dysfunction had difficulty finding dropped food. This is a simple task which could be used by the VN in practice in conjunction with a behaviour tool.
Gonzalez-Martinez et al (2013) and Heckler et al (2014) found that dogs performed better at tests with a familiar examiner. This indicates preference for the same practitioner with designated time. This fits well with an experienced nurse in a clinic setting.
In relation to nutritional studies Araujo et al (2008) suggest early supplementation prior to onset of canine cognitive dysfunction. Owners of older dogs in a clinical setting are often reluctant to alter their pet's diet (Heath et al, 2007). However Dodd et al (2003) found pet owners saw benefit in feeding a new food such as Hill's prescription b/d and Pan et al (2010) demonstrated positive outcomes when mediumchain TAG (MCT) was added to the diet. Whether diet or supplements, use of these in practice, in liaison with the VS, is achievable through monitoring and advice given in nurse-led clinics. Ingredients for these trials can be found in Table 3.
| Author | Product | Ingredients |
|---|---|---|
| Heath et al (2005) | Aktivait |
DHA/EPA, Vitamin C, N‑Acetyl cysteine, L‑Carnitine, Alpha‑Lipoic acid, Vitamin E, Acetyl‑l‑carnitine, CoQ10, Phospotidylserine and Selenium |
| Araujo et al (2008) | Senilife |
Phosphatidylserine; Ginkgo biloba, vitamin E and pyridoxine |
| Pan et al (2010) | Medium‑ chain TAG (MCT) (Nestlé PURINA) | 97% caprylic acid and 3% capric acid |
| Pan et al (2013) | Brain |
Fish oil containing DHA & EPA, Vitamin C and elevated levels of arginine, B vitamins, selenium and alpha tocopherol |
These three areas of research (behavioural or clinical signs related to cognitive dysfunction, cognition tests to measure behavioural responses and nutritional studies) into canine cognitive dysfunction allow for the development of a framework to deliver nurse-led clinics using a multi-facetted approach. A strategy for older animals providing a preventative screening programme for pre-canine cognitive dysfunction detection is possible. Use of a behavioural screening tool is vital as part of this preventative strategy. Advice given on diet and enrichment can form the initial focus for the VN alongside screening and task checks. Onward referral for veterinary advice and potential treatment would be as necessary.
In relation to cats, evidence is limited and as previously stated screening and potential treatment is extrapolated from dogs and humans (Pittari et al, 2009). Cognitive testing in cats is challenging and studies identified focused only on purpose bred cats not on household pets. While McCune et al's (2008) study showed no significant difference in position learning and finding food in three different age ranges, Milgram (2010) and Pan et al (2013) suggest cats show cognitive decline with age. Pan et al (2013) demonstrated improved cognition levels in those given a Brain Protection Blend (BPB) (Nestle PURINA) of nutrient supplements; this is worth considering in practice. Although all cats in the study appeared to have had no adverse effects, i.e. no reported signs of stress, this is in contrast to Sherman et al's (2013) study which reported signs of behavioural stress in purpose bred cats undergoing research. As in dog studies, the delayed non-matching to position (DNMP) test showed in the performance of a task; in the case of the DNMP task this demonstrates improvement of short-term memory. Heckler et al (2014) compared different cognitive tests to verify clinical feasibility and identify one test for use in practice and to monitor cognitive dysfunction. DNMP was the most sensitive test for clinical practice use. Therefore use in clinical practice for household cats may be worthwhile. However time, ethical considerations and access to household cats may be a limiting factor.
How can information be applied in practice?
First early identification of cognitive dysfunction is essential so that further investigation can take place. Veterinary nurse-led senior wellness clinics are an effective way of screening for this and other age-related risk factors and disease (Critchley, 2014). Landsberg et al (2013) suggest completion of a senior and cognitive dysfunction screening checklist (canine and feline) by the owner prior to the clinic visit which will support a more informed consultation.
Salvin et al's (2011) canine cognitive dysfunction rating scale or the simpler Fast et al (2013) four key clinical signs in dogs could form the basis for regular assessment in older pet clinics. However, unpublished research (Bowen, 2014) based on an analysis of the Salvin et al (2011) questionnaire of signs first reported by owners of dogs with cognitive dysfunction, demonstrated that if older dogs (typically 8 or more years old, according to breed) showed one or more certain behaviours at home (Table 4) then the dog may have cognitive dysfunction, particularly if these signs have become worse over recent months.
| Pace or wander aimlessly, finding it hard to settle |
| Stare blankly, or into space, as if unaware of its surroundings |
| Fail to recognise or respond to familiar people such as family and friends |
| Appear lost or confused when moving around the home or garden |
| Appear forgetful about things. For example forgetting to go to the toilet when let outside, or repeatedly asking for attention, food, or a walk |
| Bark repeatedly for no reason |
Helping owners know what to look for and recognise subtle changes in behaviour may help identify cognitive dysfunction in its early stages or even before. Gonzalez-Martinez et al's (2013) short task with dogs to find food both at home and/or within the consulting room would support the findings of the behavioural tool.
Once identified, the aim of treatment is to delay progression, return mental function to allow normal behaviour to be re-established, re-train lost behaviour and restore relationships within the household (Bowen and Heath, 2005). Diet and medication can be prescribed by the VS.
The role of the VN is to support dog and owner in the management of a condition which manifests in behavioural changes (Bennett, 2012). This may be at a time when owners find it increasingly difficult to cope with the behavioural changes in their dog and when a strain on the human–animal bond is developing (Kerrigan, 2013).
Tips on how to reduce anxiety and create a more accessible and enriched environment can help dog and owner. Anticipating needs, for example, can prevent inappropriate elimination. Additional visual, auditory, olfactory and tactile cues can help with navigation of the environment. Use of more water bowls, quiet radio, scents and rugs in different areas to identify different rooms can really improve quality of life (Bowen and Heath, 2005).
An opportunity, when medication and diet are established, to re-train learned behaviour, such as elimination, through commands is beneficial. However, it is important that owners are aware some behaviour, such as house training, may be lost (Bowen and Heath, 2005). Behavioural enrichment includes increased exercise through short walks to allow sniffing and exploration. Frequently changed toys, activity feeders to provide stimulation and increased play and interaction time are extremely useful. Offering new opportunities for exploration and extra time for play allows positive shared experiences during such a challenging time. Collectively these interventions can slow cognitive decline (Milgram et al, 2004). Simple advice to manage sleep disturbance can be helpful including additional resting places so they are more accessible and therefore usable for older pets (Bowen and Heath, 2005).
The need to explain to owners that diet/supplement therapy may take up to 6 weeks to have an effect and some medication up to 8 weeks is paramount. Similarly discussion with the owner that the need to remain positive and continue play and increased interaction is crucial; otherwise medication/diet/supplement therapy will not be successful (Bowen and Heath, 2005).
In relation to cats, Gunn-Moore et al (2007) state the older the cat the increased rate of behavioural changes. Interestingly alteration in social interactions with people and other pets appears to precede, in relation to age, behavioural alterations including aimless activity and excess vocalisation which could form the basis of screening in older felines. Gunn-Moore (2011) noted the most frequently reported behavioural problems in cats were loss of litter-box training and loud crying at night. Similar to dogs, medication, diet and environmental enrichment can delay the condition (Figures 4 and 5). Use of the Landsberg et al (2013) feline tool will support identification.
In advanced disease, VN can advise owners to reduce the size of the area of access for the cat which can reduce anxiety. Provided all needs are met such as water, food, litter box, social interactions and resting/sleeping/hiding space (Pittari et al, 2009), use of a feline appeasement pheromone can enhance a calming environment (Gunn-Moore, 2011). Well-balanced mature diets can also be advised for older cats (Gunn-Moore et al, 2007).
Further studies
Little is known about causes and risk factors for cognitive dysfunction in companion animals. This area of research requires further exploration, especially in cats. Further studies are needed to test behavioural categories (Azkona et al, 2009; Heckler et al, 2014) and a tool which assesses and identifies cognitive dysfunction in clinical settings (Salvin et al, 2011; Gonzalez-Martinez et al, 2013). Fast et al (2013) suggest studies which include more aged dogs that can be regularly reviewed during their older years as well as larger samples so duration of dietary affects can be seen (Heath et al, 2007, Araujo et al, 2008).
In cats, further research is required into the effects of age on cognitive function (McCune et al, 2008) with possible use of the adapted T-maze (Sherman et al, 2013). Determination of the optimal levels of fatty acids for maximal protection of cognitive dysfunction in cats, Pan et al (2013) identifies as another area for research and development. Clearly a regular screening tool, to assess cognition at defined ages of development, needs to be standardised and implemented in practice. This would allow for large scale studies looking at clinical signs rather than owner-based observations. However the value of the latter should not be underestimated. A countrywide campaign to educate owners to look for potential early signs of cognitive dysfunction and report these to VSs would allow for treatment regimens to be implemented. Potentially, these companion animals could then form the sample for these larger studies in clinical practice to come to fruition.
Conclusion
VNs are in a unique position to screen for potential behaviours which may indicate cognitive dysfunction in older pets. The pet should be reviewed regularly. As most companion pets are seen for annual checks by the VS, it is important to ensure that these pets are offered an option to attend an older pet clinic in between annual visits. Pittari et al (2009) advise 6 monthly checks, however 3 monthly checks could be accommodated. Overall the VN plays a key role in early diagnosis and ongoing management of cognitive dysfunction in companion animals (Warnes, 2012). It is important therefore that VNs keep up to date through continuous professional development (Royal College of Veterinary Surgeons, 2014a) and uphold the principles of the Code of Professional Conduct (Royal College of Veterinary Surgeons, 2014b). In doing this, the nursing profession can grow and flourish knowing that the welfare and quality of life of the patient — both physical and mental — is what drives excellence in care.