It’s been going this way for a while: even healthy people should be on the cholesterol-reducing drugs known as statins. That, in a nutshell, is the verdict of a study published over the weekend which found that even in people deemed to be at low risk of cardiovascular disease, treatment with rosuvastatin (Crestor) at a dose of 20 mg per day almost halved the risk of ‘vascular events’ (such as heart attack, stroke, and death from these conditions) in middle-aged and elderly men and women. Overall risk of death was down too in those taking the rosuvastatin, to the tune of 20 per cent. Average length of treatment was a shade under two years.
These results look impressive, but it does need to be borne in mind that the study population were essentially healthy. And, because of this, the risk of things like heart attacks and strokes is generally low in this population. Just to put this in perspective, the risk of vascular events was 2.2 per cent in the group taking the statin, but 2.8 per cent in those on placebo. In other words, what is known as the absolute risk reduction (as opposed to the relative risk reduction) was a little over half a percent.
It is perhaps also worth reflecting on the fact that treatment with rosuvastatin was associated, compared with placebo, with a significantly increased risk of developing diabetes. Curiously, the authors of the study say this effect could reflect the play of chance. In other words, even though there was a statistically significant enhanced risk of diabetes in those taking the statin, it may have nothing to do with the statin, and everything to do with bad luck. Curiously, the authors are not similarly circumspect about the positive effects of statins seen in this study.
But the reason for writing about this study is not so much to put the results in this context, but more to explore what these results say about the widely accepted context that cholesterol causes cardiovascular disease. On the face of it, this study strengthens this concept. But I’m not so sure.
You see this study was done in individuals whose cholesterol levels were not deemed to be risky. Individuals had to have LDL cholesterol levels of less than 130 mg/L (3.37 mmol/L) to qualify. However, to qualify for the study individuals did have to have elevated levels of a substance known as C-reactive protein (CRP). CRP is a marker for inflammation in the body, and inflammation is believed to be a key underlying process in the development of cardiovascular conditions such as heart disease and stroke.
Significant benefits were seen individuals who had elevated CRP levels, but no other major risk factors for cardiovascular disease (and LDL cholesterol levels of 100 mg/L or less). This inevitably throws up the possibility that in this study, the benefits of rosuvastatin came, at least in part, through its ability to reduce CRP levels. CRP levels actually dropped by 37 per cent on average in this study.
Cholesterol levels dropped too (LDL levels actually halved), but as the authors point out, the clinical benefit associated with this was much larger than expected. This finding also adds weight to the idea that rosuvastatin’s benefits may have been less to do with bringing cholesterol levels down, and more to do with an anti-inflammatory and/or other actions.
Previously on this site I have cited a 2006 review of the evidence regarding the relationship between cholesterol and cardiovascular outcomes such as heart attacks and strokes [2]. Having reviewed a broad range of available evidence, the authors of this review stated that: ‘no clinical trial subgroup analyses or valid cohort case control analyses suggesting that the degree to which LDL cholesterol responds to statin independently predicts the cardiovascular risk reduction.’ In other words, there is no robust relationship between cholesterol levels and degree of risk of cardiovascular disease.
This is not the only review that has found this. In another from the same year, researchers reviewed 13 studies in which statins were used in individuals who had suffered from ‘acute coronary syndrome’ (i.e. heart attack and angina). Statin therapy was found to reduce risk of cardiovascular disease, but this was independent of LDL cholesterol reduction. The authors concluded that there is no significant evidence that reduction in LDL cholesterol level explains the clinical benefits seen with statin therapy on cardiovascular disease risk [3].
And what of studies that have assessed the relationship between CRP and cardiovascular outcomes? The lead author of the recent NEJM paper was also the lead author of a paper published in 2005 that assessed data from another large statin study (the so-called ‘PROVE-IT’ study) [4]. The study concluded: Patients who have low CRP levels after statin therapy have better clinical outcomes than those with higher CRP levels, regardless of the resultant level of LDL cholesterol.
From the same year, comes another study in which the relationship between LDL cholesterol and CRP levels and development of the process which narrows the coronary blood vessels in heart disease (atherosclerosis) in individuals treated with a statin. Atherosclerosis actually regressed in patients with the greatest reduction in CRP levels, but not in those with the greatest reduction in LDL cholesterol levels [5].
Another way of unpicking the role of cholesterol in health would be to go beyond statins, and look at the effectiveness of other cholesterol reducing drugs or strategies on overall risk of death. This latest study, and others (particularly in those at high risk of cardiovascular disease) found statin therapy is associated with a reduced risk of death. A review from 2005 assessing the impact of cholesterol reducing therapy on overall mortality. Here are the results:
Statins – statistically significant reduction in risk of overall mortality
Fibrates – NO statistically significant reduction in risk of overall mortality
Resins – NO statistically significant reduction in risk of overall mortality
Niacin – NO statistically significant reduction in risk of overall mortality
Diet – NO statistically significant reduction in risk of overall mortality
Some people argue that the failure of other cholesterol-reducing strategies is because they don’t reduce cholesterol enough. I suppose that’s one potential explanation. Here’s another: cholesterol reduction doesn’t have broad benefits for health.
References:
2. Hayward RA, et al. Narrative review: lack of evidence for recommended low-density lipoprotein treatment targets: a solvable problem. Ann Int Med 2006;145:520-530
3. Hulten E, et al. The effect of early, intensive statin therapy on acute coronary syndrome: a meta-analysis of randomized controlled trials. Archives of Internal Medicine. 2008;166:1814-1821
4. Ridker PM, et al. C-reactive protein levels and outcomes after statin therapy. New Engl J Med 2005;352:20-8.
5. Nissen SE, et al. Statin therapy, LDL cholesterol, C-reactive protein, and coronary artery disease. N Engl J Med 2005;352: 29-38
