That's a question more and more people in the medical community are beginning to wonder. Anectodotal reports from several prominent physicians and medical centers have surfaced claiming that statins are associated with significant cognitive and memory impairment. In most of the stories, the memory loss was temporary and fully returned once the statin was stopped. The number of reports has reached a high enough level that the University of California San Diego is currently trying to resolve this issue through a scientific study.
Statins have been one of the most revolutionizing medicines in the treatment of heart disease. Over 25 million people are taking a statin, and this class of medication is credited with significant reductions in heart attack, stroke, and death. Not only do statins significantly lower bad cholesterol, but they have a whole range of other beneficial properties such as reducing inflammation and improving blood vessel reactivity. The most common significant side effects of statins are muscle inflammation and liver damage, but these happen relatively uncommonly.
Stories of statins causing memory loss have been present ever since the medication was first put into widespread use. When statins lower cholesterol, they can reduce the amount of cholesterol in heart artery disease. However, some cholesterol is necessary to maintain normal body functions. In the brain, cholesterol is a key ingredient of the insulation surrounding connecting nerve cells. This insulation promotes rapid communication within various parts of the brain and is important in transmitting thought and memory. It has been suggested that if total body cholesterol levels are too low, then nerve cell communication is impaired leading to impaired thought and memory. Furthermore, most people taking statins are older, and, in particular, many women are peri or postmenopausal. Menopause is a time in which estrogen levels are falling and cognitive impairments increase. Starting a statin in this stage of life may put women and the elderly at more increased risk of thought and memory problems.
To date, no reliable scientific data has shown that statins are associated with a decline in mental function. In fact, earlier this year a study showed that in ~1000 elderly Catholic clergy (two-thirds of which were women) statins did not cause a decrease in mental function nor have any relation to the development of Alzheimer's disease. Furthermore, several hundred completed studies involving statins have not shown any definitive causal link between statins and memory loss but have shown benefit in reducing heart disease.
Although large scale scientific studies have not shown a direct link between statins and memory loss, that doesn't necessarily mean that some people are not having this side effect. It's hard to argue with the story in which a person's memory became quite poor when started on Lipitor, quickly returned to normal once the drug was stopped, became poor again when challenged again with Lipitor, and then fully recovered once permanently off the medication. Scientific studies may be able to predict how a general population will respond to a medicine, but they cannot necessarily predict how an individual will respond. For now, the studies tell us that statins are generally safe and good for treating heart disease. Whether memory problems are also a result of statins waits to be officially proven.