Thanks in part to advances in the ability to prevent and treat medical problems, cats and dogs are tending to live longer and consequently more animals are showing age-related changes in their behaviour, including behaviours that owners may regard as problematic (Gunn-Moore, 2011; Landsberg et al, 2012). This is a concern because behaviours that have a negative impact on owners can be a significant risk factor for abandonment, rehoming or, in elderly animals in particular, euthanasia. In addition, subtle changes in behaviour are often the earliest indicators that an animal is developing a medical problem. Early recognition of behaviour changes and their significance in elderly animals, both by pet owners and practice staff, should enable earlier identification and treatment of medical conditions, which will significantly improve both the treatment prognosis and the animal's welfare. Increasing awareness amongst veterinary nurses of the significance of behaviour changes in elderly animals should improve the welfare of elderly animals under their care.
This article will outline why behaviour can change as animals get older, the types of behaviour changes that may be seen and how the underlying causes of these can be diagnosed. In a follow-on article the approaches to managing and treating animals showing age-related changes in behaviour will be discussed as well as preventative strategies that can reduce or delay the onset of age-related behaviour changes in cats and dogs.
Causes of behaviour changes in elderly animals
Medical problems
As cats and dogs get older they are at increased risk of developing a large number of medical problems that can affect their behaviour (Landsberg et al, 2011). In many cases these behaviour changes can be very similar to those seen in animals with cognitive dysfunction (Table 1). These can include conditions causing:
| Behaviour change | Potential medical and behavioural causes |
|---|---|
|
Development or increase in anxiety, fearfulness or phobia including:
|
Painful conditions, e.g. osteoarthritis, dental disease |
|
House soiling:
|
Conditions reducing mobility/ability to reach and/or access appropriate toileting areas including painful conditions, musculoskeletal disorders, neurological disorders etc |
|
Changes in interactions with owners and other pets including:
|
Conditions causing increased irritability including pain, inflammation, cognitive dysfunction, other CNS pathology |
|
Excessive vocalisation:
|
Sensory loss, esp hearing loss |
|
Spatial or temporal disorientation:
|
Cognitive dysfunction and other CNS pathology Sensory loss, especially if fairly acute |
|
Repetitive behaviours including:
|
Conditions causing discomfort, e.g. osteoarthritis, dental disease, abdominal pain |
| Restlessness/waking at night | Conditions causing discomfort, e.g. osteoarthritis, dental disease, abdominal pain |
Cognitive decline and dysfunction
Ageing is associated with a gradual reduction in cognitive function: the ability to perceive, process and respond appropriately to social and environmental information. This can affect behaviour in a number of different ways (see also Table 1):
| My cat… | Yes | Maybe | No |
|---|---|---|---|
| Is less willing to jump down | |||
| Will only jump up or down from lower heights | |||
| Sometimes shows signs of being stiff | |||
| Is less agile than previously | |||
| Shows signs of lameness or limping | |||
| Has difficulty getting in or out of the cat flap | |||
| Has difficulty going up or down stairs | |||
| Cries when they are picked up | |||
| Has more accidents outside the litter tray | |||
| Spends less time grooming | |||
| Is more reluctant to interact with me | |||
| Plays less with other animals or toys | |||
| Sleeps more and/or is less active | |||
| Cries loudly for no reason/to try to gain my attention Appears forgetful |
NB. Need to ensure there are no environmental reason(s) for these behaviour changes.
It can be difficult to differentiate between the signs caused by cognitive dysfunction and those caused by osteoarthritis. Both conditions ofter occur concurrently in old cats and many of the treatments for one condition will also help the other.
In the early stages of cognitive decline behaviour changes are often very subtle and may not be noticed by owners. When cognitive decline starts to impact significantly on an animal's normal behaviour this will certainly be noticed and the animal may be classed as having cognitive dysfunction. A definitive diagnosis of cognitive dysfunction can only be made post mortem, based on the presence of specific pathological changes in the brain (see below). In live animals the presence of cognitive dysfunction can only be inferred through the presence of suggestive behaviour changes, and after ruling out other potential medical and behavioural causes of those behaviour changes.
The age at which animals develop cognitive dysfunction is extremely variable. A couple of studies indicate that signs suggestive of cognitive dysfunction were shown by 5% of dogs aged 10 to 12 years, 23.3% of dogs aged 12 to 14 years and 41% of dogs older than 14 years (Salvin et al, 2010), and by 28% of cats aged 11 to 15 years and 50% of cats older than 15 years (Landsberg et al, 2010).
Learning
Animals do not stop learning as they get older: they will still learn negative associations with unpleasant events, and undesirable behaviours can be inadvertently reinforced by attention from owners, so problem behaviours can arise and be influenced by learning just as in younger animals. However an individual animal's learning ability will be influenced by the degree of cognitive decline, and also any medical problems, they have. In general, elderly animals cope less well with stress than younger animals and are more prone to developing problems associated with fear and anxiety (Landsberg et al, 2012).
In many cases elderly animals will have both medical conditions and some degree of cognitive decline or dysfunction, and both will contribute to the behaviour changes seen. Owners may also inadvertently reinforce undesirable behaviours such as repetitive vocalisation through giving attention (Landsberg et al, 2013).
Pathological changes in the brain associated with development of cognitive decline and dysfunction
The age-related decline in cognitive function in cats and dogs is associated with a number of pathological processes occurring in brain tissue, some of which are similar to the changes seen in Alzheimer's type dementia in people (Cory, 2013). These include:
Although the underlying causes of these pathological changes are not fully understood, age-related changes in cerebral blood flow and exposure to free radicals are believed to be significant factors (Gunn-Moore, 2011; Landsberg et al, 2012). Free radicals or reactive oxygen species are negatively charged molecules formed in cells as a by-product of oxygen metabolism and normally removed by the body's natural anti-oxidant defences. The balance between production and removal alters as animals age, and free radicals accumulate in cells where they cause damage. The degree to which this happens in an individual animal is influenced by a number of factors including genes, exposure to environmental pollutants, disease, chronic stress and diet (Gunn-Moore, 2011; Landsberg et al, 2012; Cory, 2013).
Diagnosing cause(s) of behaviour changes in elderly animals
Identifying behaviour changes in elderly animals
Changes in behaviour are the only clinical signs seen in animals with cognitive dysfunction, and are often the earliest signs of many other medical problems common in elderly pets (Landsberg et al, 2012). The earlier these conditions are diagnosed the better the prognosis for treatment. However owners do not always report changes in behaviour in elderly pets to veterinary surgeons or veterinary nurses in practice (Landsberg et al, 2012). There may be several reasons for this. Animals with mild cognitive decline often show fairly subtle changes in behaviour and owners may not notice them or recognise their significance (Landsberg et al, 2012). Even when animals are showing more severe behaviour changes, owners may assume these are ‘normal’ for elderly animals and may only report them to veterinary staff if they are having a significant impact on the owners' quality of life, for example if animals are waking at night, house soiling or showing aggression (Landsberg et al, 2012). Finally some owners may be reluctant to mention a behaviour problem in an elderly pet because they are concerned that it cannot be treated and that the only option is euthanasia.
It is therefore essential that veterinary surgeons and veterinary nurses specifically ask owners about behaviour changes whenever they see older pets in the surgery, although ideally owners should be asked about their pets' behaviour at every visit to the surgery from puppy or kittenhood onwards.
Screening tests such as the validated Canine Cognitive Dysfunction Rating Scale (Salvin et al, 2011), available online at http://petsci.co.uk/canine-cognitive-dysfunction-questionnaire/ or a targeted questionnaire for cats, e.g. Gunn-Moore, 2011 (Table 2) or dogs, e.g. Landsberg et al, 2012, may make it easier to identify behaviour changes suggestive of cognitive dysfunction and some other age-related medical problems.
It is also important that owners are made aware that appropriate management and treatment strategies can be very helpful in improving behaviour problems in elderly pets and that they can also slow progression of cognitive decline. These will be discussed in Part 2.
Identify and treat or rule out concurrent medical problems
Many of the medical problems common in elderly animals can cause behavioural signs very similar to those seen in animals with cognitive dysfunction and some, including circulatory problems, can directly contribute to the severity of cognitive decline. It is therefore essential that any elderly animal showing behaviour changes receives a thorough clinical examination to identify or rule out an underlying medical cause before assuming the animal has cognitive dysfunction (Landsberg et al, 2012). It is particularly important to identify and treat painful conditions in elderly animals because these can have significant negative effects on behaviour, welfare and the pet–owner relationship. However, elderly animals with cognitive dysfunction will often have concurrent medical problems that may or may not be contributing to the behaviour changes seen. Identifying and treating any concurrent medical problems such as painful conditions or hypertension can significantly improve the animal's behaviour and demeanour and also improve the prognosis for treating the cognitive dysfunction.
Identify learning-related causes for behaviour changes
It is important to identify or rule out normal learned behavioural responses and exposure to external stressors as underlying reasons for behaviour changes in elderly animals. It is important to ask owners about any changes in the pet's routine or environment that might coincide with the behaviour change: moving home, a change in the owners' work hours, the arrival of a new baby or the introduction of a new pet into the household are all potential triggers for behaviour changes. However it is also important to be aware that cognitive decline can reduce an animal's ability to cope with changes in the environment and increase the likelihood of them making learned negative associations with situations and stimuli.
Conclusion
Changes in behaviour are relatively common in elderly cats and dogs, and can include problem behaviours including aggression, house soiling, increasing fearfulness and waking owners at night. These behaviour changes can occur as a result of a number of different medical problems as well as age-related cognitive decline. Early recognition of behaviour changes in elderly animals will ensure faster diagnosis and treatment of the underlying medical and/or behavioural conditions, which should improve both the prognosis for treatment and the animal's welfare generally. However owners of elderly pets will not always mention changes in their pets' behaviour during veterinary visits. It is therefore important that veterinary nurses are aware of the significance of behaviour changes in elderly animals, and that they actively ask owners of elderly pets about their pets' behaviour generally, as well as the incidence of specific behavioural signs that could indicate the animal is developing cognitive dysfunction and/or other medical problems.