A progressive deterioration in mental ability due to degeneration of brain tissue
It is normal to become mildly forgetful with increasing age, but severe impairment of short-term memory may be a sign of Alzheimer’s disease. In this disorder, brain cells degenerate and deposits of an abnormal protein (known as amyloid plaques or tau tangles) build up in the brain. As a result of these changes, the brain tissue shrinks and there is a progressive loss of mental abilities, known as dementia.
Alzheimer’s disease is the most common cause of dementia, affecting about 417,000 people in the UK. It is mainly affects the elderly and becomes more common with increasing age: it affects about 1 in 14 people over the age of 65, and about 1 in 6 people over the age of 80. However, it can also affect younger people, and in the UK there are about 15,000 people under 65 who have Alzheimer’s disease.
The underlying cause of Alzheimer’s disease is not known in the majority of cases. In a few cases, the disease runs in families and a number of genes have been identified that are associated with development of the disease. For example, a gene known as APOE, which is on chromosome 19, is associated with Alzheimer’s disease that develops in older people (late-onset Alzheimer’s disease). Various other genes linked with Alzheimer’s disease have also been identified but all of them are rare and, overall, they are thought to be involved in fewer than 1 in 1,000 cases. People with Down’s syndrome who live into their 50s or beyond are also at increased risk of developing Alzheimer’s disease.
The first symptom of Alzheimer’s disease is usually forgetfulness. The normal deterioration of memory that occurs in old age becomes much more severe and begins to affect intellectual ability. Memory loss is eventually accompanied by other symptoms, which may include:
Difficulty in understanding written and spoken language.
Difficulty with simple arithmetical tasks, such as calculating change.
Wandering and getting lost, even in familiar surroundings.
In the early stages of the disease, people are usually aware that they have become more forgetful. This may lead to depression and anxiety (see Anxiety disorders). Over a longer period, the existing symptoms may get worse and additional symptoms may develop. These may include:
Slow movements and unsteadiness when walking.
Rapid mood swings from happiness to tearfulness.
Personality changes, aggression, and feelings of persecution.
Sometimes people find it difficult to sleep (see Insomnia) and become restless at night. After several years, most people with the disease cannot look after themselves and need full-time care.
There is no single test that can be used to diagnose Alzheimer’s disease. The doctor will discuss the symptoms with the affected person and his or her family. Tests may be arranged to exclude other possible causes of dementia. For example, blood tests may be carried out to check for vitamin B deficiencies. CT scanning, PET scanning, or MRI may be carried out to exclude other brain disorders, such as multi-infarct dementia, subdural haemorrhage, or a brain tumour. An assessment of mental ability, which may include memory and writing tests, may be used to determine the severity of the dementia.
There is no cure for Alzheimer’s disease, but acetylcholinesterase inhibitor drugs may slow the loss of mental function in some cases. Some of the symptoms that are sometimes associated with Alzheimer’s disease, such as depression and sleeping problems, can be relieved by antidepressant drugs. A person who is agitated may be given a sedative drug to calm him or her down.
Eventually, full-time care may be necessary, either at home (see Home care), and Caring for someone with dementia or in a nursing home. Caring for a person who has Alzheimer’s disease is often stressful, and carers need practical and emotional support, especially if the affected person starts to become hostile and aggressive. Support groups can help a person to cope with caring for an elderly relative with the disease. Most people with Alzheimer’s disease survive for up to 10 years from the time of diagnosis.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.