A controversial drug for Alzheimer's can reverse some of the mental deterioration experienced by people who are in the advanced stages of the disease, according to a study published today.

Relatives and many doctors have campaigned for the drug, Aricept, to be made available to people with Alzheimer's - not least because there is no other treatment for the disease, which erodes the memory. The National Institute of Clinical Excellence, which assesses the cost-effectiveness of drugs, recommended that Aricept be made available only to patients who have moderate dementia.

A study published online by the Lancet medical journal today has looked for the first time at the use of the drug in people with advanced disease, living in care homes. Bengt Winblad from the Karolinska Institutet in Sweden and colleagues recruited nearly 200 people with severe Alzheimer's and gave half of them Aricept, while the rest received a placebo for six months.

The results were positive, they say. "Donepezil (Aricept) slows and can reverse some aspects of deterioration of cognition and function in individuals with severe Alzheimer's who live in nursing homes," says Prof Winblad today.

However, in a commentary alongside the study, David Hogan of the division of geriatric medicine at the University of Calgary in Alberta, Canada, says that the patients' improvement was measured by scores in tests that may seem significant to researchers, but do not mean much to most doctors treating patients.

"Before a trial starts, we should define what will be a clinically important outcome for an individual patient and explore the use of outcome measures, such as goal-attainment scaling," he writes. "If not, we are doomed to never-ending debates about the meaning of the tea leaves at the bottom of the cup."