Metabolic syndrome is a constellation of factors (increased waist circumference, high blood pressure, elevated fasting glucose, high triglycerides, low hdl) that are associated with increased cardiovascular risk. Metabolic syndrome is often called pre-diabetes both because sugars are high and because metabolic syndrome is related to insulin resistance, the primary mechanism of type 2 diabetes. Diabetes has been generally defined as having a fasting blood sugar of greater than 126, so patients with sugars between 100-125 have also been called pre-diabetics. Like diabetes, we know that metabolic syndrome is associated with increased cardiovascular risk (increased risk for heart attack and stroke). Men with three or more components of metabolic syndrome have more than double the risk for cardiovascular disease, and women with three or more factors have almost six times the risk for cardiovascular disease.
Because diabetes is associated with such a high cardiovascular risk, and because lowering cholesterol with statins in diabetics has proven to reduce these events, current guidelines recommend that virtually all diabetics take a statin, even for those patients with normal cholesterol levels. One question which remains is whether the same should be done for patients with elevated fasting blood sugars and/or metabolic syndrome.
A recent study in the New England Journal called Glycated Hemoglobin, Diabetes, and Cardiovascular Risk in Nondiabetic Adults may give us more reason to consider thinking about using cholesterol lowering agents in patients with elevated blood sugars, even if the cholesterol is normal. The study looked at the relationship of hemoglobin A1c (HbA1c) to development of diabetes and cardiovascular risk. It was not surprising that even high end normal HbA1c's predicted development of diabetes, but what was surprising was that high normal HbA1c was strongly associated with risk for heart attack and stroke.
In the study, patients with an HbA1c of less than 5.0% had 4% relative decreased risk of cardiovascular disease compared to patients with and A1c of 5.0 to 5.5%. However, those with A1c's from 5.5 to 6.0% had a 23% increase, those with A1cs of 6.0 to 6.5% had a 78% increased risk, and those with 6.5% or greater had an almost double risk of cardiovascular disease. This suggest a strong correlation between elevated blood sugar (pre-diabetic patients) and cardiovascular risk.
In the most recent updates to the ADA guidlines published in the January 2010 edition of Diabetes Care, the ADA now defines diabetes as patients with an A1c of >6.5%, and those patients with A1c's between 5.7–6.4% have been included in a category of increased risk for future diabetes. Thus, the last group in the recent study would now be considered to already have diabetes.
This study also made me think of the JUPITER trial. The JUPITER trial is a controversial trial which I have blogged about before (see Jupiter is Out, and the News is Good! and Crestor: Get Ready to Ask Your Doctor for the CRP Test). It showed that patients with relatively normal cholesterol levels, but high levels of CRP benefited from taking 20mg of Crestor. Crestor now has an FDA indication for primary prevention of heart disease.
Interestingly in the JUPITER study, 41% of patients had the metabolic syndrome. The median A1c was 5.7 (interquartile range was 5.4-5.9). This means that about half the patients in the study had an extra 23% increase for cardiovascular disease based on A1c alone, and about 25% of patients had a 78% additional risk or higher (with the new ADA definition, there was probably not an insignificant number of patients in the JUPITER study that had an A1c above 6.5% that would now be considered to be diabetic and should have been on a statin). The reason I bring up JUPITER is because we now have a primary prevention trial in which a substantial number of patients had metabolic syndrome or elevated sugar, and this trial showed that statins were beneficial.
Thus, there are compelling arguments that can be made to suggest that patients with either metabolic syndrome or an elevated HgA1c should be on a statin (similar to diabetics) regardless of their cholesterol number.
1. In order to definitively make this case, you would need a large, randomized clinical trial of patients with metabolic syndrome (or A1c's between 5.5 and 6.5) and normal cholesterol, randomized to statin or no statin. I am hopeful that the NIH or some drug company is planning on doing this.
2. In a subgroup analysis of the JUPITER trial, the investigators looked to see whether metabolic syndrome was a factor in those patients that benefited from Crestor and didn't find a statistically significant difference. It appears that CRP levels and not sugar levels is what made the difference.
3. Though the presence of metabolic syndrome does predict cardiovascular disease, it predicts diabetes much better, and the Framingham risk score is a much better predictor of cardiovascular disease (see Metabolic Syndrome vs Framingham Risk Score for Prediction of Coronary Heart Disease, Stroke, and Type 2 Diabetes Mellitus )
Bottom Line: Elevated HgA1c levels and metabolic syndrome substantially increase risk for cardiovascular disease, and there are compelling reasons to consider statin therapy in these patients, though conclusive data is lacking. As per the new ADA guidelines, patients at risk for diabetes should be screened with a HgA1c, and if it is greater than 6.5%, these patients are now considered diabetic and should receive a statin.
Since the Framingham risk calculation is still the best predictor for cardiovascular risk, a reasonable approach might be to adjust the Framingham score for patients with HgA1c's between 5.5% and 6.5%. Currently, patients with a Framingham risk of greater than 10% are considered for more aggressive LDL goals (which usually means they need a statin). Based on the numbers from the recent New England Journal study, for patients with A1c's from 5.5 to 6.0%, more aggressive goals should be considered when these patients have a Framingham score of 8% (instead of 10%), and for those with A1cs of 6.0 to 6.5%, more aggressive goals should be considered for a Framingham score above 6%.