Memory loss and statins
Do statins affect your memory or other cognitive abilities? There have been many anecdotes and reports about statins seeming to affect mental performance. Scientific studies have not shown much in support of those ideas, at least for most patients.
Different people react to drugs differently, so nobody is saying that there is no way statins can effect the memory of some individuals.
A literature review published in the journal Pharmacology concluded that the published information on the subject is "conflicted". The press is forever quoting doctors who report their patients have concentration and memory problems while on these medications. It is anecdotal evidence of course, but scientists found statins have an effect on glial progenitor cells in the brain. While not conclusive in any way, this suggests that statins can reduce brain plasticity.
The FDA’s statement about statin safety addresses this topic with data they collected over the years. "The post-marketing adverse event reports generally described individuals over the age of 50 years who experienced notable, but ill-defined memory loss or impairment that was reversible upon discontinuation of statin therapy." http://www.fda.gov/drugs/drugsafety/ucm293101.htm
The protein amyloid and the ß-amyloid peptide (Aß) is hypothesized to be connected with Alzheimer's disease. Amyloid deposits as plaques, and experimental studies suggest links between cholesterol intake and production of amyloid in the body. However, a study shows no effects on cerebrospinal amyloid levels due to simvastin. Several studies have shown a correlation between statin use and a lower risk of dementia. A University of Michigan study in 2008 found that statins reduced the risk of cognitive impairment in people at high risk for dementia. The study looked at healty people over age 60 and found that those who were given statins developed dementia at only half the rate of those who were not given the drug.
A study of elderly people in Finland found that those who had been taking statins actually had better memories than those who had not. Further, the longer the patient had been taking the statin, the better he or she scored on tests of episodic memory. Similarly, the Sacramento Area Latino Study on Aging found that statin usage significantly lowered the risk of cognitive impairment in older people. The cases did not appear to be associated with fixed or progressive dementia.
Is the positive effect on memory due to the statins or an effect of the lower cholesterol levels? A study on people past age 90 found "hypercholesterolemia was not associated with dementia" despite suggestions to the contrary. However, the scientists still found statins helped patients avoid dementia. The speculated the mechanisms may be lower "amyloid production, neurofibrillary tangles, secondary stroke prevention, and other anti-inflammatory pleiotropic effects."
Older people are the more likely they are to be on statins and the more likely they are to have memory problems. The relationship between age and poor memory long predated the introduction of statins. It is estimated that 10% of people past age 65 have dementia. Aging people may be losing their memories at the same time they are coincidentally using statins.
Simvastatin is the most lipophilic of the statins, which may allow it to more easily cross the blood-brain barrier. "Lipophilic" means fat-loving, and the brain is composed largely of fats. Lovastatin is also lipophilic while rosuvastatin and pravastatin are hydrophilic (prefer water) and atorvastatin is somewhere in between.
The Mayo Clinic's website says that the risk of memory loss is very small compared with the benefits of statins. There is some evidence - not strong - that statins reduce the risk of cognitive impairment. A recent experiment with animals found pravastatin was effective in slowing some biochemical reactions associated with Alzheimer development.
In a meta-analysis of over 40,000 patients, researchers found no substantial evidence that statin usage affected cognition. Two large Taiwanese studies published in 2013 came down on the side of neutral-to-beneficial when it comes to the effects of statins on dementia risk. A study of 58000 patients found a inverse relationship between statin use and demenita onset prevalence. Another study of atrial fibrillation patients found a lower rate of dementia when the patient took a statin.
A recent French study found that low levels of HDL - "good" cholesterol - is correlated with the declining memory and dementia, in which case the use of statins would tend to help with cognitive skills. It is thought that HDL helps memory with anti-inflammatory and antioxidant effects. Statins do largely the same thing, so that would tend to indicate they actually help with memory. However, the memory-protective benefits of statins are probably not due to their impact on cholesterol profiles, but are due to their anti-inflammatory or other pleiotropic effects. Brain tissue contains cholesterol in disproportion to its relative mass. The most stenuous anti-statin agitators bring this fact up often as if should prove, or even strongly suggest, that statins affect the memory function. There is, however, no logical reason to draw such a conclusion.
Skeptics point to the fact that our brains are particularly rich in cholesterol as a reason statins affect memory. Up to a quarter of the body’s cholesterol is in the brain. But there is no proof that statins affect brain anatomy and no credible hypotheses for how changes in cholesterol level might affect memory, although this is partly because the mechanisms of memory are unknown.
A retrospective study of 44,000 statin patients found people who quit some statins (simvastatin and atorvastatin) were more likely to develop Parkinson's. Why this is true is unknown, because the etiology of Parkinson's is unknown. It is believed that these drugs can pass through the blood-brain barrier and get into brain cells, but how statins affect neurons is not understood.
A study at Penn State found statins may increase the risk of Parkinson’s. And that the lipophilic statins are more likely to cause problems than hydropholic ones. This runs counter to the thought - which never had strong empirical backing - that statins protect brain cells. The scientists found the impact was highest in the first few years of statin use, suggesting statins somehow trigger the onset of the disease. The conclusion came from a retrospective case-control analysis. It is not a strong finding and the medical community does not regard this one study as a reason to not administer statins to people who need them. Even the lead scientists in the Penn State study stated the results should not stop people from using statins and there is no real evidence that statins cause Parkinson’s. More research in the area is needed.