The metabolic syndrome and cardiovascular risk: implications for clinical practice

Objective: The clinical importance of the metabolic syndrome (MeS) is confused by the existence of at least three different definitions proposed by prominent organizations, and by a lack of information about the prognostic value of diagnosing a person as having the syndrome by any of the definitions. Design and subjects: We used the US National Health and Nutrition Evaluation Survey (NHANES) to determine the prevalence in the United States of the variables used to define the MeS and cardiovascular disease (CVD), and to create a simulated population that matched the US population with respect to all the important characteristics, risk factors and treatments for CVD. We then used the Archimedes model to calculate the long-term CVD outcomes for each person in the simulated population. Results: The definitions implied an increased risk of CVD of 1.5-1.6. The definitions varied considerably in their ability to identify people at risk of myocardial infarctions (MIs); the proportion of people destined to have a future MI captured by the different definitions varied from 57 to 77%. The definitions also varied widely in how well they ruled out future MIs; failure to have MeS by a definition still left a chance of a future MI ranging from 23 to 42%. The definitions differed importantly in which people they identified as having MeS; 34% of those who met the ATP definition did not meet the WHO definition, 30% of those who met the WHO definition did not meet the ATP definition and 28% of those who met the IDF definition did not meet the ATP definition. Of the components of the definitions, the most important single factor for identifying a person at risk of future CVD was high glucose, with hypertension, obesity, high triglycerides and low HDL following in that order. High glucose, by itself, was as good as any definition of the MeS in predicting risk of future MI. Whichever definition was used, individuals who met the definition varied widely in their risk of CVD. Conclusions: For assessing a particular person's risk of future CVD and for making treatment decisions a diagnosis of MeS by any of the definitions added little if anything to assessing each person's risk factors.