Alzheimer’s disease is a physical illness which damages a person’s brain. This eventually causes dementia, affecting memory and thinking. Alzheimer’s disease is the most common cause of dementia.

It’s thought that two out of three people living with dementia in the UK have Alzheimer’s disease. It’s a physical illness which, as it progresses, damages a person’s brain.

It starts many years before symptoms start to show. Eventually, Alzheimer’s causes so much damage to the brain that the person develops dementia – their thinking skills, memory and ability to carry out everyday tasks are reduced.

Age is the biggest risk factor for Alzheimer’s, as it is for most types of dementia. This means that a person is more likely to get Alzheimer’s as they get older. Above the age of 65, a person’s risk of developing Alzheimer’s doubles about every five years.

Alzheimer’s disease affects everyone differently. For most people, Alzheimer’s disease starts in and around the part of the brain involved in memory. However, in some rarer types of dementia the disease starts in a different part of the brain and so causes a different set of symptoms. This is called ‘atypical Alzheimer’s’.

The most common early symptoms include:

• memory problems
• thinking and reasoning difficulties
• language problems
• changes to how they see and hear things
• changes in mood

Early symptoms of Alzheimer’s are mild and don’t prevent someone from doing everyday activities by themselves. This is called mild cognitive impairment (MCI).

It’s often not possible at this stage to say for sure that the person’s symptoms are being caused by Alzheimer’s disease, as there could be many other causes.

The symptoms of Alzheimer’s disease will get worse over time. As Alzheimer's disease progresses, a person will need increasing support with everyday living.

The causes of Alzheimer’s disease are very complex, but one key part is the build-up of two substances inside the brain called amyloid and tau. When conditions in the brain aren’t right, these clump up and form tiny structures called plaques and tangles. These make it harder for the brain to work properly.

Over time the disease causes certain parts to become smaller. It also reduces the amount of important chemicals needed to send messages around the brain.

Eventually the brain struggles to cope with the damage and the person begins to have problems with memory and thinking. When it gets to the stage where these problems are making it difficult for the person to do everyday tasks that they used to do easily, this is called ‘dementia’.

It is very important for anyone who has worsening problems with their memory or thinking to be assessed by a health professional, which is most often their GP. If a GP thinks their symptoms may be caused by dementia, they will refer the person to a local memory service for more detailed assessment.

Alzheimer’s will usually be diagnosed by a specialist health professional. Getting an early diagnosis has many benefits, giving you time to adjust and get things you need.

There are some less common types of Alzheimer’s disease that do not cause memory problems at first. These are known as ‘atypical’ Alzheimer’s. There are four main types, which have different early symptoms:

• one mostly affecting language, called logopenic aphasia
• one causing problems with vision and working out where things are in relation to each other, called posterior cortical atrophy
• one that affects behaviour and/or thinking, called frontal variant Alzheimer’s disease
• one that causes problems with movement and sensation as well as thinking, perception and language, called corticobasal syndrome.

There are many different things that can increase a person’s chances of getting Alzheimer’s. These are known as ‘risk factors’. Some of these risk factors cannot be changed, but many others can. 

Age and genes are the biggest risk factors for Alzheimer’s, as they are for most types of dementia, and these cannot be changed. However, people can still reduce their risk by making positive changes to their health and lifestyle.

There are many ways to help someone to live as well as possible with Alzheimer's disease. For more help and support, you can contact our support line, or join our online community.