Scientists have now found that it also boosts learning and memory, but only in six-month-old mice when the dementia disorder has not progressed, according to the Mirror.
The drug had no effect on an Alzheimer's hallmark - the build up of amyloid beta protein in the brain.
Simvastatin can be bought over the counter but its effect on human Alzheimer's is still unclear, Canada's 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," study leader Dr Edith Hamel added in the Journal of Neuroscience.
Dr Simon Ridley, from the charity Alzheimer's Research UK, also noted: "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," he added.
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 Li added.