New ACC/AHA Guidelines for Statins: Calculator Overestimates Risk

Last week the American College of Cardiology/American Heart Association (ACC/AHA) published guidelines on cardiovascular risk assessment, and lifestyle changes and cholesterol-lowering treatment to reduce cardiovascular risk (J Am Coll Cardiol 2013 Nov 12 early online PDFCirculation 2013 Nov 12 early online PDF). Many DynaMed topics have been updated to incorporate these new guidelines and replace the 2002 National Cholesterol Education Program (NCEP) guidelines. For the Statins for prevention of cardiovascular disease topic 3 major issues are of exceptional interest.

1. The ACC/AHA guidelines do not identify “target” cholesterol levels as the goal when treating dyslipidemia. 

This is now consistent with guidelines from other countries (such as 2008 NICE guidelines in the United Kingdom) which recognize benefit in treatment from overall risk reduction but not specific benefit from treating to target levels. The ACC/AHA guidelines (unlike the NICE guidelines) recommend monitoring cholesterol levels on treatment, especially for the purpose of monitoring and encouraging treatment adherence.

2. The threshold for when statin therapy is recommended are much lower in the ACC/AHA guidelines than in the NICE guidelines.

The ACC/AHA guidelines recommend treatment with a 10-year risk for cardiovascular disease events > 7.5% and suggest treatment may be reasonable at a risk of 5%-7.5%, while NICE recommends statins therapy for adults with a 10-year risk > 20%. Both groups recommend statin therapy for most patients with diabetes or established cardiovascular disease.

3. Use of Pooled Cohort Equations is proposed for estimating the 10-year risk of cardiovascular disease events.

The Pooled Cohort Equations appear to overestimate cardiovascular risk. This was found in comparison to actual event rates in the 2 cohorts used for independent external validation of these equations, and was also reported in 3 large primary prevention cohorts (Lancet 2013 Nov 19 early online PDF). The DynaMed topic on Cardiovascular risk prediction includes multiple approaches for risk estimation, including links for their use and evidence supporting them.

To put this into perspective for patients:

To understand the benefits for an individual patient it is useful to estimate the absolute benefit of treatment for that patient. This can be understood as the number of patients who would need to be treated for 5 years to prevent one adverse outcome (NNT). We made estimates of the NNT for selected major adverse outcomes at different levels of predicted 10-year risk, using estimates for risk reductions derived from systematic reviews:

NNT for Statins for 5 Years:
10-year risk of CVD events 5-year NNT for CVD events 5-year NNT for myocardial infarction 5-year NNT for stroke 5-year NNT for mortality
5% 160 278 910 *
7.5% 108 186 606 *
10% 80 140 456 *
15% 54 94 304 334
20% 40 70 228 250
Abbreviations: CVD, cardiovascular disease; NNT, number needed to treat (to prevent 1 outcome)

* no apparent mortality reduction in lowest-risk patients (BMJ 2013 Oct 22;347:f6123)

Courtesty: DynaMed

 The guidelines consider risks for adverse effects to be minimal. Randomized controlled data find low rates of serious adverse events, such as rate of myopathy 1 per 10,000 person-years, and a modest increase in diabetes (NNH 255 over 4 years [Lancet 2010 Feb 27;375(9716):735]) Observational studies have reported up to 17.4% rates of statin-related adverse events (Ann Intern Med 2013 Apr 2;158(7):526)

For more information, see the Statins for prevention of cardiovascular disease topic in DynaMed.



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