Introduction

The metabolic syndrome (also known as syndrome X, or the insulin resistance syndrome) is a combination of at least three of five well-known risk factors for heart conditions. The factors consist of 'thresholds' for different tests:

• Serum triglyceride level over 150 mg/dL (1.7 mmol/L)
• Serum HDL ('good') cholesterol below 40 mg/dL (1.0 mmol/L) in men, or 50 mg/dL (1.29 mmol/L) in women
• Fasting blood sugar over 110 mg/dL (6.1 mmol/L)
• Blood pressure over 130/85 mm Hg (either number), or being on blood pressure medication
• Waist size over 40 inches (102 cm) in men, or 35 inches (88 cm) in women.

It's not surprising that having the metabolic syndrome would put one at a higher risk of later developing heart disease, and indeed this has been shown already in some studies. However, an analysis of a large clinical trial conducted in Scotland has confirmed this, and in addition shown that people with the syndrome are at a much greater risk of developing type 2 diabetes as well.

What was done

In the study, over 6,500 men with raised serum cholesterol levels were given either pravastatin (a 'statin' drug) or placebo, and followed for 5 years. During this time, coronary heart disease events, such as a heart attack or severe angina, were recorded, as well as the onset of diabetes, if it was detected.

The men were assessed for metabolic syndrome at baseline, using the thresholds given in the Introduction above, except that a body mass index, or BMI, of over 28.8 was used instead of waist measurements, as these had not been made.

One in four men was found to have the metabolic syndrome. (This isn't the same as the rate in the general population, as these men were chosen as having raised cholesterol levels.) During the 5 years, there were over 400 coronary events and 140 new cases of diabetes diagnosed.

What was found

The analysis focused on possible differences between men with and without the metabolic syndrome. Age and LDL ('bad') cholesterol levels were similar in both groups, while the C-reactive protein (CRP) was significantly raised in those with the syndrome.

Those men with the metabolic syndrome were 1¾ times more likely to have a coronary event in the 5 years period, 3½ times more likely to develop diabetes.

This level of increased risk for a coronary event was roughly equivalent to that of a 10-year increase in age, or being a current smoker. Although it may not seem very high, it was significant in a statistical sense - i.e. the results were not due to chance alone.

If the men passed 4 or 5 of the thresholds for metabolic syndrome, their chances of a coronary event were increased 3½ times, and their risk for diabetes increased almost 25 times. A raised CRP level (above 3.0 mg/dL) was found to increase the risk level too, whether the metabolic syndrome was present or not.

Taking the statin drug had the effect of reducing the coronary artery event risk in men with the syndrome down to that seen in those without the syndrome.

Comment

The important findings of this study were:

1. confirmation that having the metabolic syndrome increases the risk of coronary artery disease
2. having the metabolic syndrome increases the likelihood of developing type 2 diabetes quite dramatically
3. measuring CRP is an additional way of finding out who is at risk of developing both serious conditions

The 'take-home' message? Working on all the risk factors that make up the metabolic syndrome - overweight, high blood pressure, high blood sugar, and unhealthy lipid levels - is a worthwhile way to reduce one's chance of having a heart attack or getting diabetes in the years to come.