(NaturalNews) Cholesterol-lowering statin drugs do not provide any protection against Alzheimer's disease, according to a study conducted by researchers from the Rush University Medical Center in Chicago and published in Neurology
, the journal of the American Academy of Neurology.
"This study adds to the growing evidence that statins don't lower the risk of Alzheimer's disease," lead researcher Zoe Arvanitakis said. "The study also found no association between taking statins and a slower cognitive decline among older people."
Prior studies on animals have suggested that taking statins might lower the risk of developing Alzheimer's disease, and a human study in 2000 found that the disease was less common in those who took the cholesterol drugs. Researchers have speculated that this result might arise from the fact that cholesterol and inflammation are known to play a role in the development of Alzheimer's, and statins tend to reduce levels of both.
But a number of studies since 2000 have failed to replicate the same effect, leading many doctors to conclude that the drugs do not actually provide a benefit for cognitive health.
"There is good evidence that statins do not prevent Alzheimer's," said Dr. James Wright of the University of British Columbia, remarking on the body of current evidence.
The current study was conducted on 929 Catholic clergy members taking part in the Religious Orders Study on aging and Alzheimer's disease. All participants had no signs of dementia when the study began in January 1994. Just over 68 percent of them were female, and the average starting age was 75. The study was funded by grants from the National Institute on Aging.
The rate of statin use among the 191 participants who developed Alzheimer's
disease was approximately the same as the rate of use in the general participant pool, leading the researchers to conclude that statins had no effect on the development of the disease. A brain autopsy was also conducted on all 250 participants who died during the study, and the researchers found no effect of statins on the occurrence of brain markers of Alzheimer's disease
Strokes and Alzheimer's disease are the two primary causes of dementia, which is defined as a decrease in cognitive function greater than would normally be expected from aging.
Statin use also failed to protect against the cognitive decline associated with Alzheimer's disease
, such as memory loss. Researchers measured cognitive function through a series of 19 tests of five different measures once per year for 12 years, until the study's conclusion in November 2006. Each participant's global cognition score was derived by combining the scores for measurements of episodic memory, semantic memory, working memory, perceptual speed and visuospatial ability.
There was no association between statin use and the level of global cognition, nor was it associated with the rate of change in global cognition over time. Among only patients who developed Alzheimer's disease, statin use likewise failed to show any effect on the rate of cognitive decline.
According to Larry Sparks, director of the Roberts Laboratory for Neurodegenerative Disease Research at the Sun Health Research Institute in Arizona, the sample size of the Rush study was too small to conclusively rule out statins
as beneficial for Alzheimer's prevention. Sparks, one of the first researchers to report such a connection, says that the type of statin used might make a difference in the effect.
"Research suggests that statins that don't get into the brain may prevent or slow the progression of Alzheimer's," he said.
The Rush researchers did in fact test for any difference between two kinds of statins, depending on whether they were more or less lipophilic. Neither kind had any effect.
Sparks said he has had success in treating mild or moderate cases of Alzheimer's with statins. But Arvanitakis disagreed with this assessment.
"Physicians should not prescribe them for Alzheimer's disease," Arvanitakis said.
William Thies of the Alzheimer's Association said it is too early to totally rule out statins as beneficial for Alzheimer's. He expects a final answer from clinical trials that are currently ongoing. But he noted that as long as the issue remains unsettled, "there is no recommendation that you take statins for Alzheimer's disease."
Some researchers have speculated that early studies may have shown a cognitive benefit from statins simply due to the fact that people who are more concerned about their health appear to have a reduced risk of developing Alzheimer's disease. People who are more concerned about their health are also more likely to take statins, which may create a correlation between statin use and decreased Alzheimer's risk where no causation exists.