New Guidelines for Diagnosis and Management of Metabolic Syndrome

The American Heart Association (AHA) and the National Heart, Lung, and Blood Institute (NHLBI) have issued guidelines for the diagnosis and management of the metabolic syndrome. "The metabolic syndrome has received increased attention in the past few years," write Scott M. Grundy, MD, panel chair, and colleagues from the AHA and the NHLBI. "It consists of multiple, interrelated risk factors of metabolic origin that appear to directly promote the development of atherosclerotic cardiovascular disease (ASCVD). This constellation of metabolic risk factors is strongly associated with type 2 diabetes mellitus [DM] or the risk for this condition."

The panel found that the metabolic syndrome is a complex disorder, with no single factor as the cause. However, the most important risk factors were abdominal obesity and insulin resistance. Other metabolic risk factors are atherogenic dyslipidemia (elevated triglyceride levels and apolipoprotein B, small low-density lipoprotein cholesterol [LDL-C] particles, and low high-density lipoprotein HDL cholesterol [HDL-C] concentrations), high blood pressure (BP), high plasma glucose levels, a prothrombotic state, and a proinflammatory state. Other conditions that may promote the metabolic syndrome include sedentary lifestyle, aging, hormonal imbalance, and genetic or ethnic predisposition.

Prospective population studies suggest that the metabolic syndrome is associated with approximately a twofold increase in relative risk for ASCVD, and a fivefold increase in risk for developing diabetes.

Goals for lifestyle intervention for abdominal obesity are to reduce body weight by 7% to 10% during the first year of treatment and continued weight loss thereafter to achieve desirable weight (body mass index, < 25 kg/m2) and waist circumference of less than 40 in. for men and less than 35 in. for women. Recommended physical activity is of moderate intensity for 30 to 60 minutes five to seven days a week. Diet should reduce intakes of saturated fat (< 7% of total calories), trans fat, cholesterol levels (< 200 mg/day), and total fat (25% – 35% of total calories). Most dietary fat should be unsaturated, and simple sugars should be limited.
Other overall conclusions of the panel were that the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria for clinical diagnosis of the metabolic syndrome were robust and clinically useful, and they recommended maintaining the NCEP-ATP III criteria with minor modifications.

The NCEP-ATP III definition requires defined abnormalities in any three of five clinical measures: waist circumference, elevated triglyceride levels, HDL-C levels, BP, and fasting glucose level. Modifications recommended by the panel include adjustment of waist circumference to lower thresholds when individuals or ethnic groups are prone to insulin resistance; considering triglyceride levels, HDL-C levels, and BP to be abnormal when drug treatment is prescribed; clarifying that elevated BP refers to a level exceeding the threshold for either systolic or diastolic pressure; and lowering the threshold for elevated fasting glucose level from 110 to 100 mg per dL.

For patients with the metabolic syndrome who have a relatively high 10-year risk for ASCVD, the guidelines state that drug therapy of both major and metabolic risk factors can help lower risk. They suggest using pharmacotherapy according to present recommendations by the AHA, NHLBI, and American Diabetes Association (ADA) for individual risk factors, but not specifically to reduce risk for type 2 DM independent of treatments to prevent ASCVD.

The panel described specific treatment of metabolic risk factors for prevention of ASCVD or treatment of type 2 DM, including treatment of atherogenic dyslipidemia, hypertension, elevated glucose levels, prothrombotic state, and proinflammatory state.
"Additional research is required both to better understand the underlying pathophysiology of the metabolic syndrome and to identify new targets for therapy," the panel concludes.

Circulation. Posted online Sept. 12, 2005.

Practice Notes : The AHA and NHLBI recommends modifications to the NCEP-ATP III criteria as follows: (1) adjustment of waist circumference to lower thresholds when individuals or ethnic groups are prone to insulin resistance, (2) allowing triglyceride and HDL-C levels and BP to be counted as abnormal when a person is prescribed drug treatment for these conditions, (3) clarifying that elevated BP is defined as an elevation of either systolic or diastolic BP, and (4) reducing the threshold for elevated glucose level from 110 mg per dL or higher to 100 mg per dL or higher in accordance with the ADA revised definition of IFG.

The NCEP-ATP III and IDF have similar management guidelines for the metabolic syndrome but differ in that the IDF requires increased waist circumference to be a criterion for diagnosis and adjusts the definition of increased waist circumference to ethnicity.

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