According to a new review of studies, statins, the most successful class of cholesterol-lowering medicines, have no role in preventing Alzheimer's disease (AD).
Statins includes medications like atorvastatin (Lipitor) and pravastatin (Pravachol), which are some of the best-selling drugs in the world.
The drugs lower cholesterol by inhibiting a key enzyme used by the body to make it, which decreases cholesterol formation and helps reduce the amount of low-density lipoprotein (LDL or "bad" cholesterol).
"From these trials, which contained very large numbers and were the gold standard ... it appears that statins given in late life to individuals at risk of vascular disease do not prevent against dementia. I feel the follow-up time was sufficient to allow for an effect to appear," said lead study author Bernadette McGuinness, a senior clinical research fellow in geriatric medicine at Queen's University in Belfast, Ireland.
Many studies have shown that elevated serum cholesterol levels may lead to AD, and thus lowering them could prevent the neurological disorder.
The review comprised 26,340 participants in two major studies.
One study, the Medical Research Council/British Heart Foundation Heart Protection Study (HPS), looked at simvastatin (Zocor) use in 20,536 patients and followed them for five years.
The other study, the PROSPER trial, looked at pravastatin use in 5,804 patients, with an average follow-up of 3.2 years.
Both studies were double-blind randomized, placebo-controlled studies of statin medications in individuals at risk for dementia and Alzheimer disease and had participants between the ages of 40 and 82 in total.
The review showed no evidence that statin medications were harmful to cognition.
Also the review authors found no difference between patients receiving the medications and patients receiving placebo medications, when it came to incidence of dementia, cognitive function or performance on specific neuropsychological tests, such as a picture word-learning test.
Dr. Beatrice Golomb, of the department of family and preventive medicine at the University of California, San Diego, said that some randomized trials had shown that the net effect of statin medications was significantly adverse and others had shown it was neutral.
However, she claimed that none had shown that using statin could be favourable for cognition.
The new review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research.