MAIN CHARACTERISTICS OF ALZHEIMER'S DISEASE

Memory loss

Loss of memory can have consequences on daily life in many ways, leading to communication problems, safety hazards and behavioural problems. In order to understand how memory is affected by dementia, it is useful to consider the different kinds of memory.

Episodic memory

This is the memory people have of events in their life ranging from the most mundane to the most personally significant. Within episodic memory, there are memories classed as short term (having happened in the last hour) and those classed as long term (having occurred more than an hour ago). People with Alzheimer's disease, at the beginning of the illness, do not seem to have any difficulty remembering distant events but may, for example, forget having done something five minutes ago. Memories of distant events although not greatly affected tend to interfere with present activities. This can sometimes result in the person acting out routines from the past which are no longer relevant.

Semantic memory

This category covers the memory of what words mean, e.g. a flower or a dog. Unlike episodic memory, it is not personal, but rather common to all those who speak the same language. It is the shared understanding of what a word means, which enables people to having meaningful conversations. As episodic and semantic memory are not located in the same place in the brain, one may be affected and the other not.

Procedural memory

This is the memory of how to carry out actions both physically and mentally, for example, how to use a knife and fork or play chess. The loss of procedural memory can result in difficulties carrying out routine activities such as dressing, washing and cooking. This includes things which have become automatic. For this reason, some patients who have difficulty finding their words can still sing fairly well. Their procedural memory is still intact whereas their semantic memory (the meaning of words) has been damaged.

The Syndrome Apraxia/Aphasia/Agnosia

Apraxia is the term used to describe the inability to carry out voluntary and purposeful movements despite the fact that muscular power, sensibility and coordination are intact. In everyday terms this might include the inability to tie shoelaces, turn a tap on, fasten buttons or switch on a radio.

Aphasia is the term used to describe a difficulty or loss of the ability to speak or understand spoken, written or sign language as a result of damage to the corresponding nervous centre. This can become apparent in a number of ways. It might involve substituting a word which is linked by meaning (e.g. time instead of clock), using the wrong word but one which sounds similar (e.g. boat instead of coat) or use a completely different word with no apparent link. When accompanied by echolalia (the involuntary repetition of words or phrases spoken by another person) and the constant repetition of a word or phrase, the result can be a form of speech which is difficult for others to understand or a kind of jargon.

Agnosia is the term used to describe the loss of the ability to recognise what objects are and what they are used for. For example, a person with agnosia might attempt to use a fork instead of a spoon, a shoe instead of a cup or a knife instead of a pencil etc. With regard to people, this might involve failing to recognise who people are, not due to memory loss but rather as a result of the brain not working out the identity of a person on the basis of the information supplied by the eyes.

Communication

People with Alzheimer's disease have difficulties both in the production and comprehension of language which in turn lead to other problems. Many patients also lose the ability to read and the ability to interpret signs.

Personality change

People with Alzheimer's disease might behave totally out of character. A person who has always been quiet, polite and friendly might behave in an aggressive and ill-mannered way. Brusque and frequent mood changes are common.

Behaviour

A common symptom of Alzheimer's disease is wandering, both during the day and at night. There are a number of possible reasons for this wandering but due to communication problems, it is often impossible to find out what they are. Other symptoms affecting behaviour include incontinence, aggressive behaviour and disorientation in time and space.

Physical changes

Weight loss can occur even when the normal intake of food is maintained. It can also occur as a result of the person forgetting to chew or how to swallow, particularly in the later stages of the illness. Another consequence of Alzheimer's disease is the wasting away of muscles and once bed-ridden there is the problem of bed sores. As people age, their vulnerability to infection increases. As a result of this increased vulnerability, many people with Alzheimer's disease die from pneumonia.

A broad outline of the main features of the three stages of development.

People with Alzheimer's disease do not all suffer the same symptoms in the same order and with the same degree of severity. However, there is a general pattern of progression of the disease which makes it possible to describe three broad stages. The following description of these stages, although not exhaustive, can help carers to know roughly what to expect and to prepare themselves in advance both physically and psychologically.

Stage 1

The first stage tends to be marked by moderate memory problems, such as forgetting names and telephone numbers, but due to the mild nature of these problems, they might not be immediately noticeable. The person concerned may try to prevent others noticing the problem due to embarrassment or worry. Similarly members of the family or friends might try to play down the importance of the problem, perhaps due to the belief that forgetfulness is a natural consequence of ageing. However, the memory problems experienced by younger Alzheimer's disease sufferers are less likely to go unnoticed, particularly if they occupy a post which necessitates the use of memory.

The problem is further aggravated by accompanying difficulties with attention. A combination of these two problems may lead to difficulties accomplishing tasks involving several sub-stages and even in following the thread of a conversation which in the work situation would probably not go unnoticed for long. Another consequence is that the patient will find him/herself searching for words. In turn, although this does not generally affect the person's interest in communicating, he/she will tend to use simpler words and short sentences.

Orientation in time is not greatly affected at this stage, but patients tend to show signs of disorientation in space (wandering and even getting lost in a familiar environment such as the home). Many patients develop strange tastes (for example in clothes) and some have a preference for vivid colours. Others may show a lack of spontaneity and activity and develop a tendency to stare with a forward gaze, accompanied by a marked inability to change the position of the eyes.

Finally patients start to have problems with abstract representation. Money, for example, loses its symbolic form with the consequence that goods or a service might be paid for more than once. They find it difficult to associate geometric forms with real objects, i.e. they would not be able to reproduce a cube as it is too abstract. The above problems may be noticeable to a greater or lesser extent depending on a number of factors such as the patient's work, family, lifestyle and personality. This stage can be extremely stressful for the patient as he/she is fully aware of what is happening.

Stage 2

In the second stage, the severity of the symptoms generally leads patients to leave their job and stop driving. As a result they become more dependent on others. Memory problems become more pronounced with recollection of recent and distant events being affected, although memories for distant events generally remain intact the longest.

One consequence of this is that on seeing their grandchildren some patients remember relatives who have died, which can be disturbing and lead others to think that they are unable to differentiate between the living and the dead. Memory loss can also lead patients to believe that relatives or friends have not visited them for a long time when in fact they have just left. In addition to this, patients often have difficulty recognising their own family as the link between face and name has gone.

It becomes more difficult to interpret stimuli (touch, taste, sight and hearing). This has repercussions on daily life in the form of loss of appetite, the inability to read and visual/auditive hallucinations. Insomnia may become a problem as the distinction between day and night loses its significance. Patients tend to sleep more during the day, but less at night. The notion of time and space is affected.

Daily activities such as washing and dressing become impossible to accomplish alone due to memory loss, confusion and difficulty in manipulating objects. Movements become less and less precise and co-ordinated.

Patients become less stable on their feet and may have accidents due to double vision. Incontinence may occur either as a result of failing memory, communication problems and practical difficulties or as a result of brain damage in that the signals are no longer registered or recognised. Patients tend to suffer from brusque and frequent changes of mood. They may appear to be self centred and refuse help. They may become agitated and aggressive or pace up and down the room all day long.

Language problems become more marked, including the inability to understand the spoken and written word, as well as difficulty speaking and writing. It is not unusual at this stage for patients to constantly repeat the same words or sentence.

Stage 3

In the third stage, the patient can be said to be suffering from severe dementia. Cognitive functions are almost completely gone. The patient loses the ability to understand or use language and may simply repeat the ends of sentences without understanding what the words mean. Incontinence becomes total and there is a loss of the ability to walk, sit, smile and swallow.

The patient is more prone to pneumonia and risks bed sores if not regularly turned. He or she becomes rigid, loses reflexes to stimuli and may be agitated and irritable. Constant surveillance is clearly necessary at this stage. However, despite the severity of the symptoms at this stage, patients still tend to respond well to touch and familiar, soft voices.