Most care homes have at least some people with dementia who are being treated with anti-psychotics or tranquilisers

Dr Richard Harvey, Alzheimer's Society

He said: "Tranquilisers are the easy option.

"Quite often they are given covertly, mixed with food.

"The level of complaints suggests that probably most care homes have at least some people with dementia who are being treated with anti-psychotics or tranquilisers."

The society said that anti-psychotics drugs and newer treatments were highly effective for treating hallucinations and delusions but there was only limited evidence to show they improved behavioural symptoms.

Patients were often prescribed drugs for months or even years even though there was little evidence of long-term benefit.

For most patients, the drugs can cause severe and unpleasant side effects, including excessive sedation, increased confusion, muscle rigidity, tremors and falls.

Drug-free strategies

Research has also suggested that neuroleptic drugs, which help reduce symptoms such as delusions, cut the life expectancy of people with dementia.

The society believes alternative drug-free strategies and nursing care can replace the use of drugs for the majority of cases.

The four-year research programme, costing �270,000, will take cover 40 care homes in London, Newcastle and Oxford.

It will test the effectiveness and acceptability of alternatives to regular tranquilisers for those people with dementia who present the most serious behavioural problems.

A team will visit nursing homes and look at ways of cutting out the drugs and advise staff on alternative methods of treating difficult people.

This could involve questioning approaches to dealing with difficult behaviour by looking more closely at what causes it.

Dr Harvey said: "We want this research to change practices throught the country and throughout the world if it's proved to be effective."

More than 700,000 people in the UK have dementia and more than half have Alzheimer's disease.

Dementia affects one in 20 people over the age of 65 and one in five over the age of 80.