The Importance of Waist Circumference in the Definition of Metabolic Syndrome

OBJECTIVE: The purpose of this study was to compare the predictive ability of the National Cholesterol Education Panel (NCEP), revised NCEP (NCEP-R), and International Diabetes Federation (IDF) metabolic syndrome criteria for mortality risk, and to examine the effects of waist circumference on mortality within the context of these criteria. RESEARCH DESIGN AND METHODS: The sample included 20,789 white, non-Hispanic men 20-83 years of age from the Aerobics Center Longitudinal Study. The main outcome measures were all-cause and cardiovascular disease (CVD) mortality over 11.4 years of follow-up. RESULTS: The proportions of men with the metabolic syndrome were 19.7, 27, and 30% at baseline, respectively, according to NCEP, NCEP-R, and IDF criteria. A total of 632 deaths (213 CVD) occurred. The relative risks (RRs) and 95% CIs of all-cause mortality were 1.36 (1.14-1.62), 1.31 (1.11-1.54), and 1.26 (1.07-1.49) for the NCEP, NCEP-R, and IDF definitions, respectively. The corresponding RRs for CVD mortality were 1.79 (1.35-2.37), 1.67 (1.27-2.19), and 1.67 (1.27-2.20). Additionally, there was a significant trend for a higher risk of CVD mortality across waist circumference categories (102 cm) among men with at least two additional metabolic syndrome risk factors (P = 0.01). CONCLUSIONS: The prediction of mortality with IDF and NCEP metabolic syndrome criteria was comparable in men. Waist circumference is a valuable component of metabolic syndrome; however, the IDF requirement of an elevated waist circumference warrants caution given that a large proportion of men with normal waist circumference have multiple risk factors and an increased risk of mortality.