NO one has discovered a way to prevent the progressive deterioration of memory, behaviour and everyday functioning that define Alzheimer's disease. However, might a drug that helps people at a mild or moderate stage of the disease also benefit those with a severe case?

A study randomly assigned 248 people diagnosed with probable Alzheimer's disease to take donepezil or a placebo daily. All participants lived in nursing homes or assisted-living facilities. After six months, cognitive skills (including memory, language and social interactions) generally improved in people taking donepezil, whereas they continued to decline in those taking the placebo. Overall, the ability to perform such daily tasks as eating, dressing, turning lights on and off and getting a drink of water worsened for both groups, but less so for people taking the drug.

Who may be affected by these findings? People with severe Alzheimer's, the stage at which a person doesn't recognise family members, becomes difficult to understand and may forget how to do such previously instinctive things as swallow, walk and smile.

Caveats: Whether the results would be applicable to people not living in a care facility remain unclear; some Alzheimer's studies have shown differing results for people who live in private homes, compared with those in care facilities. Nearly all participants took other medications during the study, including analgesics, antidepressants and antipsychotics. The findings may not apply to people with forms of dementia other than Alzheimer's. About 26% of those taking the drug and 17% of the placebo group did not complete the study.

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