A common cholesterol-lowering drug may be effective against Alzheimer's if given at an early stage of the disease, new research suggests.
The findings, from a mouse study, add to laboratory evidence that cholesterol-lowering statins may prevent some of the symptoms of Alzheimer's.
Earlier work by the same Canadian team showed that the drug simvastatin improved blood flow in the brains of year-old laboratory mice with Alzheimer's.
The new study by McGill University found it also boosted learning and memory - but only in younger six-month-old animals whose disease had not progressed far.
Younger mice had higher levels of two memory-related proteins in the hippocampus, the brain's key memory centre.
In both cases, the animals received higher doses of simvastatin. Low doses of the drug can be bought over-the-counter at pharmacies in the UK.
Significantly, statin treatment had no effect on one of the hallmarks of Alzheimer's, a build up of amyloid beta protein in the brain.
The findings are published in the latest issue of the Journal of Neuroscience.
Study leader Dr Edith Hamel, from McGill University, said: "This study shows that simvastatin can protect against some of the damaging effects of Alzheimer's disease on nerve cells involved in memory, if administered early in the disease process."
However the scientists pointed out that more research was needed to find out whether humans could benefit the same way.
US Alzheimer's expert Dr Ling Li, from the University of Minnesota, said: "This article joins an increasing number of pre-clinical studies demonstrating that statins, in particular simvastatin - which easily penetrates the brain - can counteract some aspects of Alzheimer's disease, despite seeing no effects on amyloid-beta protein.
"Although several clinical trials have yet to show the benefits of statins for Alzheimer's disease, the key now is to figure out how to translate these exciting findings from bench to bedside."
Dr Simon Ridley, from the charity Alzheimer's Research UK, said: "Overall evidence suggests that statins like simvastatin do not benefit people with dementia, but this new mouse study suggests that the timing of treatment could be vital.
"Many experts believe that treatments for dementia will be most beneficial if given very early in the disease process.
"While these new findings are valuable, the benefits are shown in mice and we don't know how they will bear out in humans. There is a real need to push on with research that will boost early detection and help people with dementia get more benefit from treatments."