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UK [1]

Prevalence and incidence

When talking about demography it is important to distinguish between prevalence - the frequency with which dementia occurs in the population, and incidence - the number of new cases of dementia in a given time period.

The well established prevalence rates for dementia in the UK are:

Age (years)
40 - 65 1 in 1000
65 - 70 1 in 50
70 - 80 1 in 20
80+ 1 in 5

Projected growth in the UK

  • It is estimated that by 2010 there will be about 840,000 people with dementia in the UK
  • This is expected to rise to over 1.5 million people with dementia by 2050

A steady, rather than dramatic growth is expected over the next 25 years.

Proportions of those with different forms of dementia
Although there is some disagreement over the precise numbers, the proportions of those with different forms of dementia can be broken down:

Type of Dementia
Alzheimer's disease 55%
Vascular dementia 20%
Dementia with Lewy bodies 15%
Pick's disease and frontal lobe dementia 5%
Other dementias 5%

Younger people and dementia
Dementia in people under the age of 65 is comparatively rare. There are over 18,000 younger people with dementia in the UK

People from an ethnic minority and dementia
The proportion of older people from an ethnic minority in the UK is small, but increasing steadily as this section of the population ages. There are at least 5,000 people with dementia amongst ethnic minorities.

People with a learning disability and dementia
People with learning disabilities may experience a higher risk of dementia because of premature ageing. Also, people with Down's syndrome have an increased genetic risk of developing dementia.

Dementia worldwide
The number of people with dementia is expected to increase steadily over the next 25 years:

  • There are over 5 million people with dementia in Europe
  • There are nearly 18 million people with dementia in the world
  • By 2025 there will be about 34 million people with dementia in the world
  • By 2025 71% of people with dementia will live in developing countries

What is it?

The term dementia describes a group of symptoms caused by the impact of disease on the brain. Symptoms typically include problems with memory, speech and perception. Short-term memory is usually affected. Long-term memory may be retained.


Alzheimer's disease
Alzheimer's disease is the most common cause of dementia. During the course of the disease the chemistry of the brain changes and cells, nerves and transmitters are attacked. The disease typically begins with lapses in memory, mood swings and in difficulty finding the right words. Later the person affected may become more confused and may find it difficult to understand what is being said.

Vascular dementia

Vascular dementia describes all those forms of dementia caused by damage to the blood vessels leading to the brain. Symptoms of vascular dementia can either happen suddenly following a stroke, or over time through a series of small strokes in the brain, known as multi-infarct dementia. Symptoms may include depression or mood swings.

Dementia with Lewy bodies

This form of dementia gets its name from the tiny spherical structures made of proteins that develop inside nerve cells. Their presence in the brain leads to the degeneration and death of brain tissue, affecting memory, concentration and language skills. People with dementia with Lewy bodies may have visual hallucinations. They may also develop physical problems such as slowness of movement, stiffness and tremor.

Other forms of dementia

There are other less common causes of dementia. These include:

  • Degenerative conditions. In Pick's disease, for example, damage to brain cells is more localised than in Alzheimer's disease, usually beginning in the front part of the brain, or frontal lobe. Initially personality and behaviour are more affected than memory, but in the later stages symptoms are similar to those of Alzheimer's disease
  • Infection. Prion diseases, for example, which include Creutzfeldt-Jakob disease (CJD), are caused by infectious agents called prions which attack brain tissue. The variant form of the disease (vCJD) has been linked to BSE, a prion disease affecting cattle. The number of cases of vCJD remains low
  • People with the AIDS virus can also have dementia, typically in the later stages of the illness
  • Dementia can also be caused by the effect of toxins on the brain. General alcohol dementia is characterised by damage throughout the brain. Wernicke's encephalopathy and Korsakoff's syndrome are also caused by the abuse of alcohol, but the damage to the brain is more specific, particularly occurring in the frontal lobes
  • Finally, those people who have had a head injury with loss of consciousness may be more likely to develop dementia.
  • Dementia-like symptoms may also be caused by treatable conditions, such as severe depression, urinary infection, vitamin deficiency and brain tumour

Further information

Acknowledgements: This section has been developed with the help of the Alzheimer's Society.

[1] Alzheimer's Society (n.d.) Statistics. [accessed 29/11/12].


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