Dementia is now seen as the health and social care challenge of the 21st century, because the UK's ageing population means the numbers affected are set to soar. Figures suggest that more than a million people will have developed the disease before 2025.
The government has published a dementia strategy and appointed a dementia "tsar" to oversee services. But campaigners still say there needs to be greater commitment to tackling a condition for which there is no effective treatment.
WHAT IS DEMENTIA?
The idea that mental faculties can deteriorate with age has been recognised for centuries.
Some researchers even believe that Shakespeare's King Lear was a study of dementia.
Dementia is an umbrella term which describes a serious deterioration in mental functions, such as memory, language, orientation and judgement.
There are many types, but Alzheimer's disease, which accounts for two thirds of cases, is the most well-known.
It is named after the German scientist Alois Alzheimer who identified the condition over a century ago.
Alois Alzheimer identified the disease that bears his name 100 years ago.
Alzheimer had studied a patient at the Frankfurt Asylum called Auguste Deter. He first saw her in 1901 and followed her case until her death in 1906.
She displayed short-term memory loss and disorientation and, after her death, an examination of her brain showed she had the tell-tale protein deposits of amyloid plaques and tau tangles which characterise Alzheimer's disease.
Another form of the condition is vascular dementia, which develops when the oxygen supply fails and brain cells die.
Lewy Body dementia occurs when small structures develop in nerve cells, causing the degeneration of brain tissue.
Fronto-temporal dementia affects personality and behaviour more than memory.
All forms of dementia are progressive: as the brain becomes increasingly damaged over time, so a person's symptoms will become worse.
Although the elderly are primary victims of the disease - about a third of people over 65 die with a form of it - it also affects about 15,000 people under the age of 65.
HOW IT IS DIAGNOSED
The only truly accurate way to know whether person has Alzheimer's is to analyse their brain in a postmortem.
Trying to diagnose the condition when someone is alive can be difficult because so many of the signs are initially subtle, or shared with other illnesses.
Difficulties with everyday tasks
Changes in mood, behaviour and personality
Signs of confusion, agitation or forgetfulness are what usually first prompt a visit to the GP.
It can take weeks - or months if someone is in the early stages of the disease - to receive a clinical diagnosis.
This is because the patient needs to be monitored and tested over time to confirm it is dementia rather than another condition, such as depression or a brain tumour.
Signs of Alzheimer's disease
Orange and red areas on Spect scans show areas of highest blood flow and high brain activity
Blue areas, more evident in Alzheimer's cases, show areas of decreased flow because of decreased brain activity.
Reduced blood flow is seen as a result of the death of cells which occurs in Alzheimer's disease.
Dementia cannot be cured, although there are ways of alleviating symptoms, including psychological help, art or music therapy.
821,884 people have dementia in the UK
15,000 of those are under 65
The total affected is estimated to reach 1m by 2021
By 2051, it could reach 1.7m
Women account for two-thirds of cases
Dementia currently costs the UK £23bn a year
But most attention is paid to the role three drugs can play.
These drugs, called acetylcholinesterase inhibitors, are better known as Aricept, Exelon and Reminyl. These prevent an enzyme in the brain which aids communication between nerve cells from breaking down - which in turn may improve or stabilise the symptoms of the disease.
A controversial ruling by the National Institute for health and Clinical Excellence (NICE) stated that these drugs should only be available when Alzheimer's has progressed to its moderate stages, even though it is licensed for people in the earlier stages of the disease.
A further drug, Ebixa, which blocks a chemical known to be released in significant quantities in those with Alzheimer's, has also been licensed for use in moderate-to-severe cases in the UK, but it is not routinely available on the NHS.
A government strategy published last year set out a number of measures to improve dementia services in England, including better training for GPs and health professionals to help them diagnose people with dementia, and extending the existing network of memory clinics.
These are to act as "hubs", where people can be referred if they are suspected of having dementia. The plan is expected to cost nearly £2bn over 10 years.
But an official review by the National Audit Office has raised questions about how the strategy is being delivered, highlighting a number of concerns - from a failure to formally make the condition a national priority in the NHS Operating Framework to a lack of basic training for healthcare professionals.
It also described joint working with social care as "very patchy", leading to people with dementia being unnecessarily admitted to hospital, and going into residential care prematurely.
Campaigners say the strategy does indeed have the potential to transform lives, but only if local health authorities are forced to give dementia priority.
The government insists implementation is on track, and in January 2010 appointed a dementia "tsar" to oversee the strategy.
Scotland has set out its own priorities for dementia care, while Wales is due to set out its Dementia Action Plan later this year. A Northern Ireland Dementia Strategy is currently being developed and is expected to be released for consultation in coming months.
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