Alzheimer’s is a disease that causes dementia. It is the most common cause of dementia, accounting for about two-thirds of cases in older people.

What is Alzheimer’s disease?

Alzheimer’s disease is the most common cause of dementia, affecting around six in every 10 people with dementia in the UK. Some people can have more than one type of dementia, for example, they might have Alzheimer’s as well as vascular dementia or dementia with Lewy bodies. This is often called ‘mixed dementia’.

Alzheimer’s is not a normal part of ageing, but the chances of developing the disease do increase the older we get. The majority of people who develop the disease are over the age of 65. Sometimes, Alzheimer’s can affect younger people. It is thought that around 5% of people with Alzheimer’s are under 65, about 42,000 people. These rare cases of the disease are called early-onset Alzheimer’s. If you would like more information about early-onset Alzheimer’s, please contact us.

As we age our brains naturally shrink a little and our thought processes slow down. However in Alzheimer’s disease, changes that occur in the brain are different to the changes seen in normal ageing. These changes include the build-up of two proteins, called amyloid and tau. Although researchers don’t yet have a complete understanding of what triggers this, both proteins are involved in the development of Alzheimer’s. As the disease progresses, the protein build-up damages more and more brain cells. This damage affects how our brains work and leads to the symptoms of Alzheimer’s.

With the help of our researchers, we are learning more about why these proteins build up in the brain and how they damage brain cells. Research is underway to understand more about what happens in the brain during Alzheimer’s and find new ways to treat the disease.

What is Alzheimer's disease?

Find out more about the symptoms and causes of Alzheimer's disease, and the treatments currently available.


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Alzheimer’s Research UK has a wide range of information about dementia. Order booklets or download them from our online form.

This information was updated in May 2020 and is due for review in May 2022. It does not replace any advice that doctors, pharmacists or nurses may give you. Please contact us if you would like a version with references.

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Dementia Research Infoline

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