Yesterday, the National Institute for Health and Care Excellence (NICE) published draft proposals concerning the use of statins for the prevention of cardiovascular disease. Previously, NICE advised doctors to recommend treatment in those with a calculated 10-year risk of cardiovascular disease of 20 per cent or more. Now, NICE is proposing that this threshold will be reduced to 10 per cent.
I have not read the draft proposals, but I have read this piece in the Daily Mail penned by Professor Colin Baigent, a vocal promoter of statins and part of the Cholesterol Treatment Trialists (CTT) collaboration which has produced reviews that are frothing in their enthusiastic for statins.
In the piece in the Daily Mail, Professor Baigent is unequivocal in his support of statins: the benefits clearly outweigh any risks, even in those at relatively low risk of developing cardiovascular disease. The risks of statins, are utterly downplayed.
His comments essentially parrot the findings of his own research. Back in 2012, his group published a meta-analysis (grouping together of similar studies) of statin trials [1]. Part of this meta-analysis involved assessing the impact of statin therapy in individuals deemed to be at relatively low risk of cardiovascular events such as heart attacks and strokes. One of the stand-out findings of this study is that statins led to a statistically significant reduction in risk of ‘major vascular events’. This was even true for individuals at less than 10 per cent risk of such events over a 5-year period. This led to the suggestion that statins used might be widened to even people at low risk of cardiovascular problems. Let’s have a look at these results in a little more depth.
First of all, ‘major vascular events’ is a ‘catch-all’ term that encompasses many different potential outcomes including fatal and non-fatal heart attacks and strokes and ‘revascularisation’ procedures (such as placing tubes called stents in the coronary arteries). When a lot of different outcomes are grouped together, it makes it much more likely that a statistically significant results will emerge.
When the outcomes are narrowed a little, the results are less impressive. For example, when we look at risk of death from any vascular event (a heart attack or stroke), we find that statins did not reduce risk in individuals deemed to be at low risk (<10 per cent over 5 years). This, by the way, was even true for those who had known vascular disease.
The ‘positive’ findings from this study have, as is often the case, been expressed as relative reductions in risk. The risk of vascular events overall was 21 per cent lower for each 1 mmol/l (39 mg/ml) reduction in levels of low density lipoprotein cholesterol (LDL-C). This, by the way, is a theoretical risk reduction, based on mathematical modelling of the data. In reality, though, there is not a clear association between the degree of cholesterol reduction in trials and the clinical benefit derived from this. Thus, ‘promising’ certain reductions in risk with specific reductions in cholesterol is potentially very misleading.
And besides, even if statins and cholesterol reduction do lead to ‘significant’ reductions in risk of cardiovascular events, when overall risk is low, then a relative risk reduction might not amount to much in real terms.
We’re told by the authors this meta-analysis that treating with statins prevented 11 major vascular events for every 1000 people treated for a period of 5 years. Put another way, 91 people would need to be treated for 5 years to prevent one major vascular event. Or in other words, only about 1 per cent of people treated with statins for 5 years will benefit (and about 99 per cent won’t).
Professor Baigent and his colleagues give us some soothing reassurances about the fact that the benefits of statins vastly outweighing the risks of adverse events such as myopapthy (muscle pain and weakness). They quote of the excess incidence of myopathy as 0.5 cases per 1000 people over 5 years. However, the source they quote is based on diagnosing myopathy once the marker for muscle damage (creatine kinase) is at least ten times the upper limit of normal. Many individuals will have significant pain and weakness with much lower levels of creatine kinase. Statins are also linked with adverse effects on the liver and kidneys, and increase risk of diabetes too. Overall, adverse effects of statins affect about 20 per cent of people who take them.
The numbers of people who need to be treated with statinsfor one to benefit are big, and many more people with have adverse effects than who benefit. These are the facts, and it’s about time people some people were straight with them.
References:
1. Cholesterol Treatment Trialists’ (CTT) Collaborators. The effects of lowering LDL cholesterol with statin therapy in people at low risk of vascular disease: meta-analysis of individual data from 27 randomised trials. The Lancet epub 17th May 2012
