Metabolic Syndrome: New Guidance for Prevention and Treatment

Metabolic Syndrome and Obesity Treatment

The metabolic syndrome is a growing health problem in the United States, according to a new scientific statement by the American Heart Association and National Heart, Lung and Blood Institute.

The panel of experts who wrote the statement, published in today's Circulation: Journal of the American Heart Association, confirmed the recommendations on metabolic syndrome of the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) report made in 2001, with some modifications. The panel also clarified several issues based on new scientific evidence.

The metabolic syndrome, which consists of multiple interrelated risk factors, increases the risk for atherosclerotic cardiovascular disease by 1.5-3 fold, and raises the risk for type 2 diabetes by 3-5 fold. It affects over 26 percent of adults, or over 50 million Americans.

"The panel reviewed, affirmed and reinforced the previous statement. Metabolic syndrome is an important issue both for physicians and the general public," said Scott Grundy, M.D., Ph.D., chairman of the panel and director of the Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, Texas.

The criteria for the metabolic syndrome include:

• elevated waist circumference (abdominal obesity)

• elevated triglycerides

• reduced high-density lipoprotein cholesterol (HDL-C or "good" cholesterol)

• elevated blood pressure

• elevated fasting glucose

An individual who has abnormal levels of three of these criteria should be considered as having the metabolic syndrome.

The dominant underlying risk factors for the syndrome appear to be abdominal obesity and insulin resistance. Other conditions associated with the syndrome include physical inactivity, aging, hormonal imbalance and genetic predisposition. Certain ethnic groups, such as Hispanic Americans, are at higher risk than Caucasians. A diet rich in saturated fat and cholesterol can increase the risk of cardiovascular disease in persons with the syndrome. The increasing prevalence of metabolic syndrome in the United States can be explained largely by the growing epidemic of obesity.

The link between obesity and metabolic syndrome is most evident from the inclusion of waist circumference in the criteria. ATP III guidelines define a waist circumference of greater than 40 inches in men and 35 inches in women as one of the criteria for the metabolic syndrome.

While this measure still stands for the majority of individuals, the panel said it is now recognized that some persons who are not obese by traditional measures, nonetheless are insulin resistant and have other metabolic risk factors. This is especially true in individuals who have two parents with diabetes or one parent with diabetes or a first or second degree relative with diabetes. It also is true in individuals of Asian ethnicity, who are more prone to insulin resistance. In individuals who are genetically predisposed to insulin resistance, a marginally increased waist circumference of 37 - 39 inches in men and 31 - 35 in women may place them at greater risk.

Thus, the panel states that an increased waist circumference, while providing a solid diagnostic tool, is not necessary for a diagnosis of metabolic syndrome, if other criteria are present.

"If there are three other clinical criteria present, then the diagnosis of metabolic syndrome can be made without an increased waist circumference," said Grundy.

The levels of these other risk factor criteria that need to be met for diagnosis of the metabolic syndrome are:

• triglycerides of 150 mg/dL or higher;

• an HDL ("good") cholesterol lower than 40 mg/dL for men and lower than 50 mg/dL for women;

• a blood pressure level of 130/85 mm Hg or higher;

• a fasting glucose of 100 mg/dL or higher.

Most persons with metabolic syndrome are insulin resistant, which means that insulin action on glucose and fat metabolism is abnormal. Often, these individuals also have increased levels of inflammatory markers and a tendency to have blood clots, both of which predispose a person to heart attack and stroke.

The latest scientific statement allows for adjustment of the waist circumference to lower thresholds in individuals or ethnic groups, such as Asian Americans, who are prone to insulin resistance. In addition, it suggests that triglyceride and HDL-C levels + blood pressure be counted as abnormal, even when a person is on drug treatment for these risk factors. It clarifies that definition of elevated blood pressure as the level that exceeds the threshold for either systolic (the upper number) or diastolic (the lower number) blood pressure. (130/85).

The latest scientific statement brings the ATP III criteria for the metabolic syndrome in line with the American Diabetes Association's (ADA) lowering of the levels of fasting glucose required to be considered impaired. This adjustment reduces the threshold for elevated fasting glucose from more than 110 milligrams per deciliter down to 100 mg/dL in accord with the ADA's revised definition of impaired fasting glucose (IFG).

"The ADA advised that lowering the threshold would pick up more patients who would go on to develop diabetes," said Grundy. "We accepted that as defining."

The updated AHA/NHLBI diagnostic criteria maintain ATP III waist circumference thresholds for Americans. For most Americans, a waist circumference of 35 inches or more for women and 40 inches or more in men counts as being abnormally high.

There is ever increasing obesity in Americans, he said. "People are becoming overweight or obese early in life and therefore are developing metabolic syndrome earlier, increasing their risk of cardiovascular disease."

The primary goal of clinical management of the metabolic syndrome is to reduce the risk for atherosclerotic cardiovascular disease, and the risk of type 2 diabetes in patients who have not yet developed clinical diabetes, the panel said. If these conditions are present, treatment of metabolic syndrome must be intensified.

Grundy stressed the importance of the joint American Heart Association and National Heart, Lung, and Blood Institute statement, saying that it provides a more in-depth discussion and justification behind the diagnosis of the metabolic syndrome.

"This report strengthens the position that metabolic syndrome is important" said Grundy. "The American Heart Association and the National Heart, Lung, and Blood Institute strongly recommend that each of the standard cardiovascular risk factors should be treated appropriately. But this is not enough in our society where obesity and physical inactivity are becoming increasingly prevalent risk factors, in addition to well-known risk factors such as high cholesterol, high blood pressure, diabetes and tobacco abuse."

NHLBI Director Elizabeth G. Nabel, M.D., said, "This statement should serve as an alert to physicians that it is vitally important to identify and treat the growing number of people with metabolic syndrome. For individuals with this syndrome, lifestyle treatment - weight control and increased physical activity - is the primary therapy for lowering their risk factors and reducing the long-term risk for heart disease." - DALLAS, Sept. 13