Background and Purpose—The purpose of this study was to compare definitions of metabolic syndrome with regard to their prediction of stroke and coronary heart disease incidence.

Methods—The study comprises 4041 men and 3812 women of 6 Finnish and Swedish cohorts aged 25 to 74 years at baseline. Hazard ratio was estimated applying Cox regression analyses adjusting for cohort, cholesterol, and smoking and using age as a time scale. A paired homogeneity test was performed to compare the differences.

Results—A total of 113 (47) ischemic and 43 (15) hemorrhagic stroke and 235 (50) coronary heart disease events were accumulated in men (women). Hazard ratios (95% CIs) for ischemic stroke in men were 1.59 (1.09 to 2.32), 1.52 (1.01 to 2.28), 1.16 (0.77 to 1.74), and 1.27 (0.87 to 1.86), respectively, for the World Health Organization, National Cholesterol Education Program, National Cholesterol Education Program revised, and the International Diabetes Federation definitions of metabolic syndrome, and in women 2.20 (1.15 to 4.19), 2.68 (1.47 to 4.87), 2.31 (1.27 to 4.20), and 1.91 (1.05 to 3.49), respectively. The corresponding hazard ratios (95% CIs) for coronary heart disease were 1.57 (1.21 to 2.04), 1.51 (1.15 to 1.99), 1.63 (1.25 to 2.13), and 1.46 (1.12 to 1.89) in men and 1.32 (0.69 to 2.51), 1.54 (0.85 to 2.79), 1.81 (1.02 to 3.21), and 2.47 (1.37 to 4.45) in women. None of the definitions of metabolic syndrome predicted hemorrhagic stroke. There was no difference between definitions of metabolic syndrome and between a full definition and its individual components.

Conclusions—Metabolic syndrome as well as its individual components predicted the incidence of the ischemic stroke and the coronary heart disease equally well and should be treated equally as well.