Including Insulin Resistance in the Definition of Metabolic Syndrome

Reilly M, Wolfe M, Rhodes T, et al.: Measures of insulin resistance add incremental value to the clinical diagnosis of metabolic syndrome in association with coronary atherosclerosis. Circulation 110:803-809, 2004

What is the problem and what is known about it so far?

As the number of people that are overweight or obese increases, so does the number of people with metabolic syndrome -- a group of conditions that includes a large waist size, high blood pressure, high levels of fat in the blood, and poor control of blood glucose levels.

The National Cholesterol Education Program III (NCEP III) and the World Health Organization have each come up with a definition for metabolic syndrome. NCEP III’s definition does not include a measurement for insulin resistance (the body's inability to use insulin). Some people think that this may cause doctors to overlook patients that have insulin resistance, which puts a person at risk of getting metabolic syndrome.

The researchers in this study wanted to see if people with insulin resistance were being overlooked by doctors who followed the NCEP III definition of metabolic syndrome.

Who was studied?

A total of 443 men, between the ages of 40 and 51 years and 397 women between the ages of 44 and 57 were studied. None of the participants had diabetes, cardiovascular disease (disease of the heart and blood vessels), or were related to each other. All had a family member that had heart and blood vessel disease diagnosed at an early age.

How was the study done?

Researchers took blood samples from the participants to determine their cholesterol, glucose, and insulin levels.

What did the researchers find?

A total of 27% of men and 22% of women had metabolic syndrome according to the NCEP III definition. When using the World Health Organization's definition, 15% more were classified as having metabolic syndrome. Including insulin resistance in the definition of metabolic syndrome identified more people at risk of developing cardiovascular disease.

What were the limitations of the study?

The study included mostly white participants. Therefore, results may not apply to the general population.

What are the implications of the study?

Doctors and scientists may want to consider refining the definition of metabolic syndrome. Tests of glucose and insulin levels in the body may be useful for diagnosing people at risk of disease.