Alzheimer’s disease
Information
The word dementia is used to describe a group of symptoms – these include memory loss, confusion, mood changes and communication difficulties. Dementia is caused by diseases that affect the brain. Alzheimer’s disease is the most common cause of dementia.
In this section:
What is Alzheimer’s disease?
It’s natural for the brain to shrink a little with age, and many people notice their thinking becomes slower.
But Alzheimer’s disease is linked to different and more serious changes in the brain than those seen in normal ageing.
Alzheimer’s is not a normal part of ageing, but older people are more likely to develop it. Most people who have Alzheimer’s are over the age of 65. This is called ‘late onset’ Alzheimer’s.
But younger people can also develop Alzheimer’s.
At least three in every 100 people with Alzheimer’s in the UK are under 65. This is called ‘young onset’, or early-onset, Alzheimer’s disease.
While the symptoms of young onset Alzheimer’s disease are similar to those of late onset Alzheimer’s, more unusual symptoms can develop too. So, younger people often find it takes longer to get a diagnosis.
The impact of young onset dementia can be different – people are often working, have financial commitments like a mortgage, and may have children still living at home.
What happens in the brain in Alzheimer’s disease?
Alzheimer’s disease is linked to the build-up of two proteins in the brain, called amyloid and tau.
Everyone has amyloid and tau in their brains. But in Alzheimer’s, harmful forms of the proteins become sticky and clump together.
Amyloid builds up between brain cells. Tau builds up inside the cells.
Researchers are still trying to find out exactly what triggers these proteins to build up in the first place. But we do know that these proteins are linked to more and more damage to brain cells over time. This damage affects how our brain works and leads to dementia symptoms.
Research is the only way we'll find new ways to prevent, diagnose and treat dementia and scientists need your help. Without people volunteering to take part in research, finding a cure would be impossible.
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Dementia information
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This information was updated in May 2026 and is due for review in May 2028. 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 referenced copy.
This information is produced with support from The Perfume Shop who had no input into the content.
