Recently, the International Diabetes Federation (IDF) consensus group published a new definition of metabolic syndrome for identifying individuals at high risk for cardiovascular disease (CVD) (1). The high-sensitive measurement of C-reactive protein (hs-CRP), a marker of chronic low-grade inflammation, can also be used in the risk assessment of CVD (2). We investigated whether the new IDF (1), National Cholesterol Education Program (NCEP) (3), and World Health Organization (WHO) (without microalbuminuria) (4) definitions differ at the epidemiological level regarding the strength of their association with elevated hs-CRP (>3 mg/l) (2) among a population of 992 subjects (438 men) born in 1945 and living in the City of Oulu, Finland.

The prevalence of metabolic syndrome was 31, 17, and 19% according to the IDF, NCEP, and WHO criteria, respectively, in women. Among men, the corresponding prevalences were 19, 15, and 24%, respectively. Among women, IDF-, NCEP-, and WHO-defined metabolic syndrome were significantly associated with the increased risk (adjusted risk ratio 1.77 [95% CI 1.40–2.23], 2.00 [1.59–2.53], and 2.07 [1.65–2.60], respectively) of having elevated hs-CRP in analysis after adjustment for smoking, alcohol consumption, physical activity, and educational status. Among men, the corresponding risk ratios were 1.10 (0.76–1.58), 1.87 (1.38–2.54), and 2.23 (1.69–2.94).

In sex-specific receiver-operating characteristic curve analysis, in women, the largest area under curve (AUC) was that of BMI (0.7547), being statistically significantly superior to all other components of metabolic syndrome (P < 0.05) regarding their association with elevated hs-CRP. The AUC of homeostasis model assessment of insulin resistance (HOMA-IR) (0.6749) was, per se, the second best but did not differ statistically significantly from triglycerides (0.6333), HDL cholesterol (0.6269), or fasting glucose (0.6136). In men, the AUC of BMI (0.6305) was the highest value but did not differ significantly from HOMA-IR (0.6284), fasting glucose (0.6089), triglycerides (0.5902), or HDL cholesterol (0.5825). As in women, the AUC of waist circumference, waist-to-hip ratio, and blood pressure were significantly inferior to that of BMI in men (P < 0.05).

In this middle-aged general population, BMI associated most closely with hs-CRP. In addition, HOMA-IR, fasting glucose, and lipid parameters were moderately associated with hs-CRP in both sexes, albeit being inferior to BMI in female subjects. Interestingly, the other measurements of obesity were significantly inferior to BMI.

Inflammation plays an important role in the development of disturbances in both glucose metabolism and CVD and is intimately related to several difficult-to-measure components of metabolic syndrome (5). In our study, concerning inflammation, IDF criteria did not give any improvement compared with the NCEP or WHO criteria. Instead, among men, the IDF definition tended to be inferior to the other two definitions of the syndrome. In addition, BMI and HOMA-IR, components not included in the IDF and NCEP definitions of metabolic syndrome, were closely associated with elevated hs-CRP. If other population studies confirm our finding about a weaker association between the IDF definition of metabolic syndrome and CRP levels, especially among men, the new criteria should be further considered by including hs-CRP or replacing waist circumference by BMI given that elevated hs-CRP levels have been shown to add to the prognostic information of the NCEP defined metabolic syndrome for cardiovascular events (5).

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