Is low cholesterol linked to increased cancer risk? Cholesterol 10.

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I have put this at the top in the interests of balance.  Dr Emberson is utterly confident that statins cause no cancer risk.  It is worth noting that Dr Emberson says all the studies analysed were 5 – 6 years long.

Pharma companies regularly produce studies showing how their beloved statins lower cancer risk – they have much to gain by proving this and much to lose if the opposite should ever dare be proved.  I have found 3 different studies, one on rats that showed that lipid-lowering drugs;  these are statins and fibrates 1 , caused cancer in rats and dates from 1996.  The second is an article from 2009 reviewing a worrying study that did apparently show an increased cancer risk from statins, and the third a study done in Hong Kong on type 2 diabetics who did not take statins; the study aimed to look at cancer levels in relation to LDL levels – ie is a low LDL associated with cancer?  I am just going to quote from the studies.

From the study ‘Carcinogenicity of lipid-lowering drugs’.

Data Synthesis.  All members of the two most popular classes of lipid-lowering drugs (the fibrates and the statins) cause cancer in rodents, in some cases at levels of animal exposure close to those prescribed to humans.  In contrast, few of the anti-hypertensive drugs have been found to be carcinogenic in rodents.  Evidence of carcinogenicity of lipid-lowering drugs from clinical trials in humans is inconclusive because of inconsistent results and insufficient duration of follow up.

Conclusions:  Extrapolation of this evidence of carcinogenesis from rodents to humans is an uncertain process.  Longer term clinical trials and careful post marketing surveillance during the next several decades are needed to determine whether cholesterol-lowering drugs cause cancer in humans.  In the meantime, the results of experiments in animals and humans suggest that lipid-lowering drug treatment, especially with the fibrates and statins, should be avoided except in patients at high short-term risk of coronary heart disease.2

The problem is that cancer takes time to develop.  It is not like catching a cold; the tissues have been under attack for many years before the cancer finally develops in humans, hence the comment that trials on humans need to last for many years to be of any validity.  It is also worth noting that the authors recommend statins only be used by those with a high short-term risk of heart attack, which goes contrary to the desire of the drug companies to put statins in the drinking water.  And certainly once prescribed statins, the assumption is that they will be taken for the rest of your life, with dire warnings about what will happen if you come off them.

The second study, ‘Lipid-lowering drugs and risk for cancer’, the abstract says:

The suspicion that lipid-lowering drugs might increase the risk for cancer has been present for three decades and has been the reason for intense debate and several attempts to reanalyze data from clinical trials.  Recently, the results of the Simvastatin and Ezetimibe in Aortic Stenosis study sparked new interest in this problem, as the intense lipid-lowering therapy seems to have increased the number of cancers compared with the control group.  This article gives an overview of the clinical evidence from trials and observational studies.  As of now, the evidence is inconclusive, but there does not appear to be a reason for serious concern with short-term therapy.  Whether statins and other lipid-lowering drugs will increase the risk of cancer when used over several decades is at present unknown.3

So over the 13 years between these two studies, they are still querying long term use of statins, with the emphasis on short-term therapy being deemed safe, but long term questionable. And this study clearly says it takes decades to tell whether there is an increased cancer risk – not 5 -6 years.

And so we have the final study which was deliberately done on people who are ill, but not on statins. These people had type 2 diabetes which increases the risk of them having a heart attack, amongst other woes, so they are a prime group to be prescribed statins. The link between having low LDL cholesterol levels and developing cancer still hangs in the air.  Of course, there is a world of difference between having low LDL cholesterol levels and being very healthy, between LDL cholesterol levels dropping because of illness and between LDL cholesterol levels being artificially lowered by statins.

The overall finding of this trial was that LDL cholesterol levels had a V shaped curve in relation to cancer risk.  Quoting from the Interpretation:

Our findings have important clinical implications.  A high LDL cholesterol level in patients with type 2 diabetes implies not just high risk for coronary artery disease but possibly an increased risk of cancer.  A low LDL cholesterol level is not necessarily associated with optimal clinical outcomes but is predictive of cancer and death.4

From elsewhere in the text they say that “Those with cancer were more likely to have an LDL cholesterol level of less than 2.80mmol/L or a level of at least 3.80mmol/L”.  And so this study certainly says there is a link between low – and high – LDL  cholesterol levels and developing cancer.

So make of this what you will.   Personally, I’m going with the rats.

  1. Fibrates are another form of lipid (fat) lowering drugs.  Some stop cholesterol synthesis in the liver and some cause more rapid breakdown of cholesterol []
  2. Newman TB,  Hulley SB. Carcinogenicity of lipid-lowering drugs.  JAMA 1996 Jan 3; 275 (1); 55-60 Abstr []
  3. Pedersen TR, Lipid-lowering drugs and risk for cancer.  Curr Atheroscler. Rep 2009 Sep; 11 (5):350-7 Abstr []
  4. Yang X, So WY, Ko GTC et al Independent associations between low-density lipoprotein cholesterol and cancer among patients with type 2 diabetes mellitus.  CMAJ Aug 26, 2008 vol. 179. no 5 []

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