Metabolic syndrome is characterized by interrelated risk factors for cardiovascular disease (CVD) and diabetes, including dysglycemia, hypertension, raised triglyceride levels, low HDL cholesterol levels, and obesity, specifically central adiposity. Patients with metabolic syndrome are twice as likely to develop CVD over the next 5 to 10 years when compared with those without it. In addition, metabolic syndrome has been associated with a five-fold increase in risk for type 2 diabetes.

Clarifying the Definition

To unify the diagnostic criteria for metabolic syndrome, the International Diabetes Federation (IDF) recently issued a scientific statement in conjunction with the National Heart, Lung, and Blood Institute, American Heart Association, World Heart Federation, International Atherosclerosis Society, and International Association for the Study of Obesity. The statement, published in the October 19, 2009 issue of Circulation, defines terminology and criteria related to metabolic syndrome in an effort to clarify incongruencies presented by different organizations over the past decade. “It’s our hope that this joint statement will eliminate confusion and assist physicians with the identification and treatment of patients who have metabolic syndrome,” says Robert H. Eckel, MD, FAHA, a co-author of the scientific statement.

Metabolic syndrome was first defined by a group at the World Health Organization in 1998; it emphasized insulin resistance as the major underlying risk factor. In 2001, the National Cholesterol Education Program Adult Treatment Panel-III (ATP III) characterized the syndrome as the presence of three of five risk factors (abdominal obesity, elevated triglycerides, low HDL cholesterol, high blood pressure, and elevated fasting glucose) with or without evidence of insulin resistance. Subsequently, the IDF established an alternative definition that required a threshold waist circumference to identify the syndrome. “Our joint statement has essentially merged these definitions into one,” Dr. Eckel says. “Although the levels of waist circumference still need to be defined for various populations worldwide, a consensus in the medical field regarding the clinical definition of metabolic syndrome is important to better identify relative risk and related interventions.”

Major Changes

The IDF previously considered elevations in waist circumference mandatory when defining metabolic syndrome; the ATP III did not. “It’s important to emphasize that syndromes don’t include all of the above but, rather, some of the above,” explains Dr. Eckel. “Now, waist circumference is just one of five criteria that physicians can use when diagnosing metabolic syndrome.” Patients with three of the five criteria are considered to have metabolic syndrome (Figure 1).

Furthermore, there has been no agreement on the clinical definition of abdominal obesity as assessed by the measurement of waist circumference in previous recommendations from various organizations (Figure 2). Substantial differences—as much as 8 cm—existed in waist circumference recommendations between the IDF and ATP III. “With the publication of this statement,” Dr. Eckel says, “the criteria for elevated waist circumference have been amended and are now based on population- and country-specific definitions. This was a major goal, but there is still work to be done. Hopefully, this amendment will assist in the collection and evaluation of cross-sectional and longitudinal data on waist circumference cut-points for different gender and ethnic groups.”

The Role of Patient Education

From the patient education perspective, the joint statement notes that it is critical to share with individuals that they have a series of components that predict increased risk for diabetes and CVD. However, Dr. Eckel notes that physicians should not be overly consumed with spending time educating patients on the five criteria for the diagnosis of metabolic syndrome. “Instead, we recommend that clinicians communicate the presence and clustering of risk factors,” he says. “At that point, we need to emphasize the need for lifestyle modifications as the first line of defense against metabolic syndrome. Therapeutic interventions should then be considered for treatment based on the various clinical risk factors that comprise the metabolic syndrome. As clinicians gain greater clarity on the interconnectedness of the syndrome and become armed with means to correlate that to future risk of diabetes or CVD, there is hope that we can improve outcomes.”

More to Come

According to the joint statement, it is expected that new expert groups will be formed to assess the evidence with regard to waist circumference thresholds and associated risk in the future. “As organizations continue to collaborate on adequately defining metabolic syndrome, it’s recommended that current waist thresholds for various populations be used for the time being,” says Dr. Eckel. “Some new data are available for different ethnic groups, but many groups are advising to await the outcomes of the deliberations of other health organizations. The process is evolutionary. In the meantime, further studies exploring the relation of waist circumference thresholds to metabolic risk and CVD outcomes in different populations are encouraged. We’ll also continue to recommend the use of waist measurement as a useful screening tool in primary care settings.”