A deterioration in mental ability due to disorders affecting the brain

  • More common over the age of 65
  • Sometimes runs in families
  • Lifestyle as a risk factor depends on the cause
  • Gender is not a significant factor

Dementia is a combination of memory loss, confusion, and general intellectual decline. The affected person may not realize that there is anything wrong, but his or her condition is usually distressing for close friends and family. Poor memory alone is not a sign of dementia because some memory impairment is a natural part of aging. Dementia is relatively common in elderly people, with an estimated 1 in 10 people in the UK over the age of 65 affected to some degree. Although dementia is usually progressive and cannot be treated, in a few cases the underlying cause is treatable. An elderly person with severe depression may seem to have dementia because the conditions have similar features, such as forgetfulness.

What are the causes?

The underlying abnormality in dementia is a decline in the number of brain cells, resulting in shrinkage of brain tissue. Alzheimer’s disease, which occurs mainly in people over 65 and may occasionally run in families, is the most common cause of dementia. In multi-infarct dementia, blood flow in small vessels of the brain is blocked by clots. Interruption to the brain’s blood supply due to a stroke may also sometimes result in dementia. Less common causes of dementia include other brain disorders such as Huntington’s disease, Creutzfeldt–Jakob disease, and syphilis. People with Parkinson’s disease may also eventually develop dementia but it is thought that the Parkinson’s disease alone is not responsible for the dementia.

Dementia may also occur in young people. For example, people with AIDS (see HIV infection and AIDS) may eventually develop AIDS-related dementia. Long-term abusers of alcohol are at risk of dementia because of direct damage to the brain tissue and because their poor diet often leads to vitamin B1 deficiency. Severe vitamin B1 deficiency can cause the brain disorder Wernicke–Korsakoff syndrome. In pernicious anaemia (see Megaloblastic anaemia), there is a deficiency of vitamin B12 due to impaired absorption in the digestive tract. A severe deficiency of this vitamin can result in dementia. Dementia may also be associated with repeated head injuries. Rarely, underactivity of the thyroid gland (see Hypothyroidism) may cause symptoms that resemble dementia.

Brain activity in dementia

These PET scans show a large area of normal activity in the brain of a normal person compared to reduced activity in the brain of a person who has dementia.

What are the symptoms?

The symptoms may develop gradually over a few months or years, depending on the cause. They may include:

  • Impairment of short-term memory.

  • Gradual loss of intellect, affecting reasoning and understanding.

  • Difficulty engaging in conversations.

  • Reduced vocabulary.

  • Emotional outbursts.

  • Wandering and restlessness.

  • Neglect of personal hygiene.

  • Urinary incontinence.

In the early stages of the disorder, a person is prone to becoming anxious (see Anxiety disorders) or depressed due to awareness of the memory loss. As the dementia gets worse, the person may become more dependent on others.

What might be done?

The doctor may arrange for the person to have tests to look for the underlying cause and to exclude other disorders. If a treatable underlying cause is found, treatment of that cause may improve or even cure the dementia. However, such cases are rare and the treatment of dementia is based on management of the symptoms and, if possible, slowing the progression of the condition. For example, depression may be treated with antidepressants, and drugs called acetylcholinesterase inhibitors may slow the progression of Alzheimer’s disease.

A person who has dementia usually needs support at home and may eventually need full-time care in a nursing home. Carers may also need support (see Caring for someone with dementia and Home care).

Self-help: Caring for Someone with Dementia

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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