What causes dementia? Five facts you need to know

For every 10 people with dementia, 6 have Alzheimer’s disease. Symptoms of Alzheimer’s disease include changes in memory, becoming lost in familiar places, low mood, difficulty communicating, and hallucinations.

Two proteins, called amyloid and tau, build up in the brain in Alzheimer’s disease. These two proteins are thought to damage brain cells, which causes symptoms of Alzheimer’s disease.

In the early stages of Alzheimer’s disease, damage to an area of the brain called the ‘hippocampus’ occurs. This is the area of the brain responsible for our memory. So, when the hippocampus becomes damaged in Alzheimer’s disease this leads to memory problems, one of the first dementia symptoms people experience.

Vascular dementia is the second most common cause of dementia and accounts for roughly 2 in 10 cases. This type of dementia is caused by damage to the blood vessels in the brain. It can lead to thinking and movement problems, and personality changes that worsen overtime.

Another common type of dementia is dementia with Lewy bodies. This type of dementia affects 1 or 2 in every 10 people with dementia. Dementia with Lewy bodies can cause symptoms that include changes in alertness and attention, movement problems, visual hallucinations and sleep disturbances.

FTD, sometimes called Pick’s disease, is thought to account for less than one in 20 dementia cases. FTD affects the front and sides of the brain, called the frontal and temporal lobes. These areas of the brain control our behaviour, emotions, speech and understanding of language.

So the damage caused by FTD can lead to symptoms that include personality changes, inappropriate behaviour and communication problems. You can read more about frontotemporal dementia on our dementia information pages here.

Some people have what is known as mixed dementia. For example, having both Alzheimer’s disease and vascular dementia at the same time. The number of people with mixed dementia is unknown, however some research suggests that the prevalence of mixed dementia might be more common than previously thought.

People with mixed dementia may have a wide variety of symptoms that can be difficult to manage. You can read more about the ways that dementia can affect everyday life here.

Each area of our brain is responsible for a different function. For example the front of the brain, called the frontal lobe, allows us to make decisions and is responsible for our personality and behaviour.

Different diseases that cause dementia tend to damage different areas of the brain in the early stages. Early symptoms are related to what the damaged part of the brain is responsible for. This is why the first signs and symptoms may vary between people with different types.

However, all types of dementia are progressive and as time goes on more areas of the brain become affected. In most cases this leads to a person needing more support with everyday life and tasks like washing, housework and managing finances.

In the diagram below you can see the different ‘lobes’ of the brain and what they are normally responsible for.

A rarer type of dementia called Posterior Cortical Atrophy (PCA) affects the occipital lobe at the back of the brain. One of the first symptoms people with PCA notice is visual problems, like not being able to judge distances and seeing shapes and distortions that are not there.

You can read more about the different types of dementia here.