Cholesterol-busting statins may lower the odds of suffering from a heart attack or stroke, but they don't appear to ward off dementia as researchers had hoped, a new review of clinical trials suggests.

"There is really no evidence that statins do prevent dementia, especially in elderly people (age 70 and older)," says Bernadette McGuinness, a geriatrician at Queen's University in Belfast, Ireland, and co-author of the study published today in The Cochrane Library.

McGuinness and her colleagues analyzed the findings of two large clinical trials probing the health effects of statins: the Medical Research Council/British Heart Foundation Heart Protection Study (HPS), which investigated the effects over five years of simvastatin (Zocor) in 20,536 patients, and The Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) trial, which followed 5,804 patients taking pravastatin (Pravachol) for an average of 3.2 years. Participants in these trials ranged in age from 40 to 82. In both studies, the odds of developing Alzheimer's and other forms of dementia were about the same among patients taking statins and not taking statins, McGuinness says.

Earlier research has suggested that statins might help reduce the risk of developing Alzheimer's by lowering cholesterol, which helps in the production of beta-amyloid protein (the suspected culprit in the disease), says Benjamin Wolozin, a neuroscientist at Boston University.

Laboratory studies have shown, for example, that when neurons (nerve cells) are exposed to statins, they produce less beta-amyloid, and epidemiological studies have suggested that taking statins may lower the chances of developing Alzheimer's and other forms of dementia by as much as 70 percent, he notes. But this new analysis of clinical trials provides strong evidence that statins do not stave off these diseases, says Wolozin (who actually holds a patent on the use of stains for preventing and treating Alzheimer's and thus stands to lose by making such a statement).

Moving forward, he says, scientists should focus not on statins but on promising treatments for the disease, including Eli Lilly's LY450139 gamma-secretase inhibitor, which blocks the proteins responsible for making beta-amyloid and is currently in clinical trials. (Wolozin says he has no financial or other ties to Eli Lilly). 

Image © iStockphoto/annedehaas

UPDATE (4/15/2009): A user "cas" raises a good point: the studies did indeed have short follow-up times. McGuinness told us there is still insufficient evidence to know whether giving people statins in their 40s and 50s might protect against dementia decades into the future—much longer studies would be needed.