Definition of Metabolic Syndrome
Report of the National Heart, Lung, and Blood Institute/American Heart Association Conference on Scientific Issues Related to Definition
Scott M. Grundy, MD, PhD; H. Bryan Brewer, Jr, MD; James I. Cleeman, MD; Sidney C. Smith, Jr, MD; Claude Lenfant, MD; for the Conference Participants*
he National Cholesterol EducationProgram’s Adult Treatment Panel III report (ATP III)1 identified the metabolic syndrome as a multiplex risk factor for cardiovascular disease (CVD) that is deserving of more clinical attention. The cardiovascular community has responded with heightened awareness and interest. ATP III criteria for metabolic syndrome differ somewhat from those of other organizations. Consequently, the NationalHeart, Lung, and Blood Institute, in collaboration with the American Heart Association, convened a conference to examine scientific issues related to definition of the metabolic syndrome. The scientific evidence related to definition was reviewed and considered from several perspectives: (1) major clinical outcomes, (2) metabolic components, (3) pathogenesis, (4) clinical criteria for diagnosis, (5)risk for clinical outcomes, and (6) therapeutic interventions.
2 diabetes. When diabetes becomes clinically apparent, CVD risk rises sharply. Beyond CVD and type 2 diabetes, individuals with metabolic syndrome seemingly are susceptible to other conditions, notably polycystic ovary syndrome, fatty liver, cholesterol gallstones, asthma, sleep disturbances, and some forms of cancer.
Components ofMetabolic Syndrome
ATP III1 identified 6 components of the metabolic syndrome that relate to CVD:
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Abdominal obesity Atherogenic dyslipidemia Raised blood pressure Insulin resistance glucose intolerance Proinflammatory state Prothrombotic state
Clinical Outcomes of Metabolic Syndrome
ATP III viewed CVD as the primary clinical outcome of metabolic syndrome. Most individuals whodevelop CVD have multiple risk factors. In 1988, Reaven2 noted that several risk factors (eg, dyslipidemia, hypertension, hyperglycemia) commonly cluster together. This clustering he called Syndrome X, and he recognized it as a multiplex risk factor for CVD. Reaven and subsequently others postulated that insulin resistance underlies Syndrome X (hence the commonly used term insulin resistancesyndrome). Other researchers use the term metabolic syndrome for this clustering of metabolic risk factors. ATP III used this alternative term. It avoids the implication that insulin resistance is the primary or only cause of associated risk factors. Although ATP III identified CVD as the primary clinical outcome of the metabolic syndrome, most people with this syndrome have insulin resistance, whichconfers increased risk for type
These components of the metabolic syndrome constitute a particular combination of what ATP III terms underlying, major, and emerging risk factors. According to ATP III, underlying risk factors for CVD are obesity (especially abdominal obesity), physical inactivity, and atherogenic diet; the major risk factors are cigarette smoking, hypertension, elevated LDLcholesterol, low HDL cholesterol, family history of premature coronary heart disease (CHD), and aging; and the emerging risk factors include elevated triglycerides, small LDL particles, insulin resistance, glucose intolerance, proinflammatory state, and prothrombotic state. For present purposes, the latter 5 components are designated metabolic risk factors. Each component of the metabolic syndromewill be briefly defined.
Abdominal obesity is the form of obesity most strongly associated with the metabolic syndrome. It presents clinically as increased waist circumference.
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