Results of a five-year study conducted by the Alzheimer’s Research Trust in Britain found that dementia and Alzheimer’s patients were dying an average of half a year earlier than otherwise when they were prescribed these drugs, known as neuroleptics. As a consequence, researchers said the chance dying early was doubled when the drugs were used.

Medical experts say neuroleptics should be used only "as a last resort" on the most severely agitated or violent patients. However, the UK research indicated that the drugs are being prescribed for as many as 40% -- or about 150,000 -- of all Alzheimer’s patients in UK nursing homes.

The lead researcher on the project, Professor Clive Ballard of King’s College in London, noted that patients with dementia are three times more likely to have a stroke if they take the drugs.

"It is very clear that even over a six-month period of treatment, there is no benefit of neuroleptics in treating the behavior in people with Alzheimer's disease when the symptoms are mild," Ballard told the Trust’s conference in Edinburgh, Scotland.

Ballard and colleagues studied 165 residents with Alzheimer's disease at more than 100 UK nursing homes who were on a neuroleptic drug. The drugs studied were risperidone, chlorpromazine, haloperidol, thioridazine and trifluoperazine.

During the study, researchers stopped the drugs for half of the patients and put them on a placebo. They described the results as "striking:" At the end of the second year, 78% of the dummy pill group was still alive compared with 55% of those who had continued to use neuroleptics. At 36 months the figures were 62% versus 35%, and at 42 months 60% versus 25%.

Still, the researchers couldn’t pin down a cause for the impact of neuroleptics. "We don’t know what the mechanism is and we need to explore it further," said Professor Robin Jacoby of Oxford University, one of Ballard’s research colleagues.

When informed of the test results, Neil Hunt, chief executive of the Alzheimer's Society in the UK, said: "It is a disturbing revelation that confirms some of our worst fears about neuroleptics, which have been the subject of numerous health warnings."

Hunt added: "It is a national scandal that people are being sedated in this way."