Few drugs are more widely known and prescribed than the statins, which are designed to lower elevated blood cholesterol. These drugs are indisputably effective in reducing low-density cholesterol, or LDL - the so-called "bad" cholesterol - that has been linked to an increased risk of heart attack, ischemic stroke and peripheral artery disease.

So prevalent has the use of these drugs become that, in 2005, 144.5 million statin prescriptions were written in the US alone, representing sales in excess of $16 billion. Just one such drug, Lipitor (atorvastatin), made by Pfizer, not only represents 44 percent of all US statin prescriptions, but is the number one selling drug in the world.

Since the first statin, Mevacor, was introduced in 1987, data on the safety and effectiveness of these drugs have accumulated. There are presently 17,000 articles on statins in the peer-reviewed literature.

Statins can have some well-documented adverse effects, notably muscle pain, weakness and fatigue, elevation of liver enzymes, and occasionally headache and nausea. For the people most likely to benefit from statins, however, the potential side effects need to be weighed against the cardiovascular protection that these drugs are known to provide.

The medical consensus is that statins are generally safe and effective. They almost certainly will lower your LDL, and relatively few people are affected by adverse effects such as muscle damage (which may be prevented by taking conezmye Q10 supplements). On balance, the benefits seem to outweigh the risks.

But until recently the risk-vs-benefit equation has not factored in the question of cancer. Does the use of statins to lower LDL increase, decrease or leave unaffected one's risk of particular cancers, or cancer in general? The evidence here is maddeningly contradictory. On the one hand, a number of studies from good research centers have concluded (a) that there is no evidence of any association between statins and an increased risk of cancer; and (b) that, in fact, statins may actually reduce the risk of certain types of cancer. On the other hand, there have been several studies - from equally reputable institutions - suggesting exactly the opposite - i.e., that statin use may indeed be associated with an increased risk of cancer. Settling this uncertainty is obviously an important public health issue given the vast numbers of people taking these drugs.

So, what is the current state of the evidence concerning statins and cancer risk?

First of all, to clarify, there are many different statins. Here are the most popular brands:

Simvastatin = Zocor
Lovastatin = Mevacor
Fluvastatin = Lescol

Pravastatin = Pravachol
Atorvastatin = Lipitor
Rosuvastatin = Crestor

The first three are classified as hydrophobic drugs, the second three as hydrophilic. As we shall see, these distinctions are important in relation to cancer risk.

The following selected examples illustrate the current contradictory evidence on this subject:

• A 2004 study in the Lancet reported on participants in the Scandinavian Simvastatin Survival Study (4S). This trial investigated cause-specific mortality as well as cancer incidence five years after formal closure of the trial. No difference in cancer incidence or mortality was found between the group of patients taking statins and the group taking placebo (Strandberg 2004).
• A group of Spanish researchers from the University of Barcelona reported that their case-control study of 2,362 patients had uncovered evidence of an important protective effect of statins against lymphoma (Fortuny 2007).
• An analysis of data from the large-scale Women's Health Initiative showed that while hydrophilic statins such as Pravachol, Lipitor and Crestor did not confer any reduction in breast cancer risk, the hydrophobic statins such as Zocor, Mevacor and Lescol were associated with an 18 percent reduction in the relative risk of breast cancer.
• Boston University epidemiologists reviewed the relationship between statin use and the risk of 10 different major cancers. Again, the results were inconclusive. "The present data do not support either positive or negative associations between statin use and the occurrence of 10 cancer types," the authors wrote (Coogan 2007).
• The same team of epidemiologists analyzed data on statin use for 1,809 colon cancer patients and matched controls. Writing in the Journal of the National Cancer Institute, the epidemiologists concluded that there did not appear to be any association between statin use and the risk of colon cancer (Coogan, Smith 2007).

All of this would argue that statins do not increase the risk of cancer and may, in select instances, decrease that risk. However, as we shall see next week, the picture is not consistently bright, and some cardiologists are themselves warning that aggressive statin use might indeed be associated with increased incidence of cancer.

To be concluded next week, with references.