The Big Question: It was discovered 100 years ago, but has treatment of Alzheimer's progressed?

Why are we asking this now?

One hundred years ago today, on 3 November 1906, Alois Alzheimer, psychiatrist and pathologist, presented the first case of the disease that later came to bear his name in Tubingen Germany. The patient, Auguste D, developed dementia in her 50s and was so restless and confused that doctors prescribed balneotherapy - day long immersion in a lukewarm bath - to soothe her. When she was at her worst they knocked her out with chloroform.

Today, treatment has changed, but little else. Alzheimer's disease is estimated to affect 25 million people worldwide, and the numbers are rapidly rising as the population ages. Doctors no longer use lukewarm baths, but may try soothing them with music, aromatherapy, pet therapy or a variety of cognitive and behavioural techniques.

Despite extraordinary medical advances in the last 100 years, there is not much to celebrate in relation to Alzheimer's. The quality of care depended then, as now, on the skill of the clinical team. The main change has been the introduction of drugs to control the worst symptoms, such as agitation and restlessness. But a cure remains a distant dream.

A review of the disease published in The Lancet today concludes: "Although the practice of care may have changed the core principles have remained the same."

What is Alzheimer's disease?

It is a condition you would not wish on your worst enemy. It strips people slowly of their memory, their personality and eventually their humanity. It is a progressive, neurodegenerative disorder that is incurable and irreversible.

Iris Murdoch and Ronald Reagan are among the best known sufferers. Murdoch's last novel, Jackson's Dilemma, published a year before she was diagnosed in 1996, showed early signs of the disorder with a dwindled vocabulary and simpler grammar when compared with the rich language of her earlier novels Under the Net and The Sea, The Sea.

The condition is caused by an accumulation of "plaques and tangles" - protein deposits - in the brain which may interfere first with the semantic system, causing "word-finding difficulty". No one is quite sure what causes the plaques and tangles or why they produce the typical symptoms of dementia - loss of memory, confusion and agitation.

Dementia affects over 750,000 people in the UK. More than half (55 per cent) have Alzheimer's disease. A further 20 per cent have vascular dementia caused by mini-strokes which disrupt the blood supply to the brain. Vascular dementia is commonest in people with heart disease and high blood pressure.

The remaining 25 per cent of cases of dementia have a range of causes, some of which are rare. In all there are 200 types of dementia which are commonly misrepresented by the common label Alzheimer's disease.

How is it distinguished from the ordinary effects of ageing?

With difficulty. The test for Alzheimer's is examination of the brain for the presence of plaques and tangles - which can only be conducted post mortem. Accurate diagnosis while the patient is living therefore depends on the clinical skill of the doctor.

As a rule of thumb, anyone whose memory starts to cause them problems with the activities of daily living should see their GP. There is likely to be a medical reason such as depression, vitamin deficiency or the effects of other medications. If so, the effects can be reversed - and can result in a miraculous improvement.

If the cause is not obvious, the GP may refer the patient to a memory clinic for further investigation, where a diagnosis of Alzheimer's may be made on the basis of memory tests. A major problem is that people are so terrified of Alzheimer's that they don't go to the GP - even though many, whose memory loss has other causes, could be helped.

Can I do anything to prevent it?

Wear a nicotine patch. Studies have shown that nicotine, the addictive drug in cigarettes, can help prevent Alzheimer's. Taking up smoking is not recommended, however, as it increases the risk of heart disease and stroke, raising the likelihood of vascular dementia which would more than cancel out the reduced incidence of Alzheimer's.

More seriously, eating a diet rich in fruit and vegetables, taking plenty of exercise and keeping mentally active are all recognised effective strategies against Alzheimer's and other forms of dementia. A large US study published in April concluded that eating a Mediterranean diet reduced the risk of the disease by 40 per cent.

Playing chess, Sudoku or similar games are thought to offer protection, but the evidence is limited. Staying socially engaged, with friends or family, is seen as a more important way of keeping alert. Drinking alcohol in moderation and keeping blood pressure under control are also important. "What is good for the heart is good for the brain," says The Alzheimer's Disease Society.

What treatments are available?

This is a touchy issue. Four drugs, which have been available for a decade, are claimed to halt the progression of the disease. In 2001 they were approved for use on the NHS by the National Institute for Clinical Excellence and an estimated 54,000 patients are currently taking them.

In 2005 Nice reviewed its earlier decision and last month ruled that three of the drugs - cholinesterase inhibitors called donepezil (Aricept), galantamine (Reminyl) and rivastigmine (Exelon) - should be withheld in the early and late stages of the disease and only prescribed to those with "moderate" disease. The fourth drug memantine (Ebixa) was banned altogether.

The decision provoked uproar among patients' groups who protested that it was taken on cost grounds. Although the drugs appear relatively cheap at £2.50 a day, they only work in one in five patients and it is impossible to say in advance who will benefit. The Alzheimer's Disease Society says: "These drugs make an amazing difference to some people's lives and those who benefit should not be penalised because they don't help everyone."

What hope is there for a cure?

There are two stages to finding a cure. The first is to halt the progression of the disease, the second is to reverse it. Some, limited progress has been made on the first (see above). The second is an aspirational target rather than a realistic goal as the brain has no capacity to repair itself.

A number of drugs are in final Phase III trials. The latest hope is the development of a vaccine that might halt the disease in its early stages. First trials in humans had to be abandoned after side effects emerged, but a modified vaccine is under development. A blood test for Alzheimer's is also being developed which would aid early diagnosis, identify patients for treatment and help research.

Scientists one day hope to stimulate stem cells to replace neurones lost as a result of the disease. A recent study provided the first evidence that stem cells are active in the brain in response to changes caused by the disease. But the research is in its early stages and scientists say it is too soon to predict the outcome.

Alzheimer's Society Dementia Helpline 0845 3000 336 www.alzheimers.org.uk