What are dementia and Alzheimer's and how common are they?

The UK is trialling blood tests to see if they can accurately diagnose Alzheimer's disease and other forms of dementia sooner.

The hope is that more people will be able to access care, support and new drug treatments at an earlier stage.

Dementia is a symptom found in many diseases of the brain.

Memory loss is the most common symptom, particularly the struggle to remember recent events.

Others can include changes to behaviour, mood and personality, becoming lost in familiar places, or being unable to find the right word in a conversation.

It can reach the point where people don't know they need to eat or drink.

Alzheimer's is by far the most common of the diseases that cause dementia.

Others include vascular dementia, dementia with Lewy bodies, fronto-temporal dementia, Parkinson's disease dementia, amyotrophic lateral sclerosis and the newly discovered Late.

The first signs of Alzheimer's disease tend to be lapses in memory.

This could include forgetting recent conversations, losing things, forgetting names or repeatedly asking the same question.

There can also be changes in mood such as greater levels of anxiety or confusion.

The NHS website has information on common symptoms.

Alzheimer's is mostly a disease of old age - one in six people over the age of 80 develop it.

Early onset (also known as young onset) Alzheimer's is relatively rare. Still, 5% of Alzheimer's cases are in people under 65.

A much smaller number of people are affected in their 30s and 40s.

The only known risk factor for getting Alzheimer's at a young age is if close relatives also had early onset disease. There is no known way of preventing it.

There is no proven way of stopping yourself from getting dementia.

However, research suggests that one in three cases could be prevented by lifestyle changes, including:

It is not completely clear why doing these things can help protect the brain.

Do these lifestyle factors actually stop the process of dementia in the brain? Or do they prepare the brain for dementia, so that it can compensate for longer and symptoms don't emerge?

Yes, it can be - but that's not the whole story.

Broadcaster Fiona Phillips was 61 years old when she was diagnosed with this form of dementia.

She has described how Alzheimer's "decimated" her family - and having a parent or sibling with Alzheimer's increases your risk of developing the disease.

But having relatives with the disease does not mean you are fated to develop it.

And being in a family untouched by Alzheimer's does not mean you will not develop it.

For the first time, drugs have been proven to slow the pace of Alzheimer's disease in clinical trials.

Donanemab and lecanemab target amyloid in the brain during the early stages of the disease.

Amyloid builds up in the spaces between brain cells, forming plaques that are one of the characteristics of the disease.

However, the benefit of these drugs does not appear to be huge and they do not stop or reverse the disease.

These drugs have not yet made the leap from scientific studies to routine hospital use.

Fiona Phillips is taking part in trials of a drug called miridesap at University College Hospital in London. This involves injections in her stomach every day for a maximum of 12 months.

The aim of the trial is to find out whether the drug, which removes a protein called SAP (serum amyloid P component) from the brain, can stop amyloid plaques from damaging brain cells.

The researchers think this could be part of the process of the development of Alzheimer's disease.

Patients with mild Alzheimer's disease have been recruited to the DESPIAD trial, which also includes tests on brain function.