Does the new International Diabetes Federation definition of the metabolic syndrome predict CHD any more strongly than older definitions? Findings from the British Women's Heart and Health Study

Aims/hypothesis: We compared the associations between three definitions of the metabolic syndrome and CHD risk. The definitions studied were the new International Diabetes Federation (IDF) definition, and those of the World Health Organization (WHO) and the National Cholesterol Education Programme (NCEP). Our aim was to determine whether the magnitudes of the associations for any of the syndrome definitions are greater than for the individual components. Materials and methods: A prospective cohort study of a random sample of 3,589 British women who were aged 60-79 years and free of CHD at baseline was performed. Among these women there were 194 incident cases of CHD (40 of them fatal) during 15,778 woman-years of follow-up. Results: Insulin resistance (homeostasis model assessment), triglyceride levels, systolic blood pressure, waist and waist-to-hip ratio were positively and linearly associated with CHD risk; HDL cholesterol was inversely associated with risk. All three definitions of the metabolic syndrome were modestly and similarly (to each other) associated with CHD risk. The age-adjusted hazard ratio (95% CI) was 1.32 (1.03, 1.70) for IDF syndrome, 1.45 (1.00, 2.10) for WHO syndrome, and 1.38 (1.00, 1.93) for NCEP syndrome. Adjustment for smoking, inactivity and life-course socioeconomic position resulted in attenuation of these associations to 1.25 (0.96, 1.61), 1.31 (0.90, 1.90) and 1.27 (0.90, 1.79), respectively. The magnitudes of the associations for individual components of the syndrome were similar to those for any of the syndrome definitions. Conclusions/interpretation: The metabolic syndrome, defined by any of the three methods, is only modestly associated with CHD risk in this study of older women. Life-course socioeconomic position appears to be an important confounder in the association of the metabolic syndrome with CHD risk.