NPC Archive Item: Statins for all patients with diabetes?

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Cholesterol Treatment Trialist’s Collaborators. Efficacy of cholesterol-lowering in 18,686 people with diabetes in 14 randomised trials of statins: a meta-analysis. Lancet 2008;371: 117–25

What is the background to this?
This meta-analysis, which was published in the Lancet considers whether statins are as beneficial at reducing the risk of various outcomes (e.g. myocardial infarction [MI], death from coronary heart disease, stroke) in patients with diabetes as they are in patients without diabetes, and whether the benefits depend on baseline characteristics (e.g. history of vascular disease or lipid profile).

What does this study claim?
In patients with diabetes, per 1.0 mmol/L reduction in LDL cholesterol, the following results were seen:

  • 13% relative risk reduction (RRR) in vascular mortality (RR 0.87, 99%CI* 0.76 to 1.00; p=0.008)
  • 21% RRR in major vascular events (RR 0.79, 99%CI* 0.72 to 0.86; p<0.0001)
  • 22% RRR in coronary death or MI (RR 0.78, 99%CI* 0.69 to 0.87; p<0.0001)
  • 25% RRR in coronary revascularisation (RR 0.75, 99%CI* 0.64 to 0.88; p<0.0001)
  • 21% RRR in stroke (RR 0.79, 99%CI* 0.67 to 0.93;p=0.0002)
  • Results were similar to those obtained in patients without diabetes, at least in terms of relative risk reductions.

    After five years, for every 1000 patients allocated statin therapy, 42 (95%CI 30 to 55) fewer people with diabetes had major vascular events per mmol/L LDL cholesterol reduction. As one would expect, the absolute benefit was larger among those who had vascular disease at baseline than those who didn’t (57 [95%CI 34 to 80] vs. 36 [95%CI 23 to 49], respectively). The authors also found that the benefit of statins seemed to be related to the absolute LDL cholesterol reduction produced by statin therapy and suggested that treatment guidelines which recommend treating to targets might need to be reviewed.

    The authors conclude that statin therapy should be considered for all individuals with type 1 or type 2 diabetes who are at sufficiently high risk of vascular events.

    How does this relate to existing guidance?
    The study results provide further evidence to support the NICE technology appraisal on statins for the prevention of cardiovascular (CV) events. NICE recommends that the decision to initiate statin therapy in people with diabetes should be made where a clinical assessment has estimated that the CV disease risk is likely to be equivalent to at least 20% over 10 years.

    So what?
    As discussed in an accompanying editorial, although the meta-analysis has limitations, the results of this study are reassuring and there is no need to change current practice regarding statins in patients with diabetes. The editorial also points out that treatment decisions should be based on a patient’s baseline risk of having an event in the first place and therefore the absolute benefit they are likely to attain from the statin; other factors such as life expectancy, co-morbidity and quality of life should be taken into account; and patients with diabetes should be encouraged to follow a healthy lifestyle.

    Clinicians should continue to perform CV risk assessment in patients with diabetes (either clinically or using an approved assessment tool). While the majority of people with diabetes will fulfil the criteria for consideration of a statin (CV risk greater than 20% over ten years) some will not. Even those who do may choose not to take a statin and may prefer to undertake other, non-drug methods of risk reduction. Certainly, other factors should not be forgotten e.g. smoking cessation, blood pressure control, antiplatelet therapy, and blood glucose control.

    For further information on the treatment of type 1 and type 2 diabetes please visit the cardiovascular floor on NPC.

    Study details

    Design: meta-analysis of 14 randomised trials of statin therapy

    Patients: 18,686 patients with diabetes (1,466 type1 and 17,220 type 2)

    Intervention: statin therapy to reduce LDL cholesterol

    Comparison: effects on various clinical outcomes with each trial weighted by the absolute LDL cholesterol difference in the trial at the end of the first year of follow-up

    Outcomes: the results (shown above) are reported as the effects per 1.0mmol/L reduction in LDL cholesterol

    Sponsorship: The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or the writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. Some members of the writing committee have had the costs of participating in scientific meetings reimbursed by the pharmaceutical industry, but none has accepted honoraria or consultancy payments.

    *Note that these results are quoted using 99% confidence intervals (99%CIs), rather than the usually seen 95%. This essentially means that if these results were applied to the general population, then 99 people out of 100 would have a result within the range quoted. In essence this means that the range for 99%CIs will be broader than for 95% CIs and they are more statistically robust.

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