The word dementia is used to describe a group of symptoms – including memory loss, confusion, and communication difficulties. Alzheimer's disease is the most common cause of dementia.

What is Alzheimer’s disease?

Alzheimer’s disease affects around six in every 10 people with dementia in the UK.

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. In Alzheimer’s disease, two proteins, called amyloid and tau, build up. Although we don’t yet have a complete understanding of what triggers this, research suggests that the build-up of these proteins damage more and more brain cells over time. This damage affects how our brains work and leads to the symptoms of Alzheimer’s.

Alzheimer’s is not a normal part of ageing, but the chance of developing the disease increases as we get older. Most people who have Alzheimer’s are over the age of 65, this is called late onset Alzheimer’s.

Sometimes, Alzheimer’s can affect younger people too. It’s thought that over 42,000, or at least five in every 100 people with Alzheimer’s are under 65. These rare cases of the disease are called young onset Alzheimer’s disease, and are more likely to have a genetic cause. Find out more about young onset Alzheimer's disease here.

Have you or a loved one recently been diagnosed with Alzheimer's disease?

If you have been diagnosed with Alzheimer's disease in the last two years and would like to share your experience to help shape our work please get in touch via 

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 2022 and is due to be reviewed in May 2024. It was written by Alzheimer’s Research UK’s Information Services team with input from lay and expert reviewers. Please get in touch if you’d like a version with references or in a different format.

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