Across the three studies (n = 20,581), 1,783 incident CVD events occurred over 9 years of follow-up. In the overall sample, the optimal systolic and diastolic blood pressure and triglyceride cut points were lower than those in existing definitions, whereas the glucose cut point was identical (). Within demographic subgroups, the optimal cut point varied by component and subgroup.
Empirically derived cut points and associated discrimination performance statistics for metabolic syndrome components by demographic subgroups
The presence of ≥3 components at levels above the optimal cut point (below the optimal cutpoint for HDL cholesterol), identified in , provided the highest sum of sensitivity and specificity, and two empirically derived metabolic syndrome definitions were created: 1) three or more components using cut points derived in the full sample (uniform cut point definition) and 2) three or more components using demographic subgroup-specific cut points.
More people were categorized as having metabolic syndrome using the empirically derived definitions (48.3% for uniform cut points and 51.0% for subgroup-specific cut points) compared with the ATP III (38.4%), IDF (35.6%), or Harmonized (46.0%) definitions. The empirically derived definitions, using uniform and subgroup-specific cut points, had higher sensitivity but lower specificity (0.65/0.53 and 0.67/0.50, respectively) versus the ATP III (0.53/0.63), IDF (0.51/0.66), or Harmonized (0.64/0.56) definitions. The empirically derived definition with uniform cut points provided little improvement over the ATP III (RIDI 5% [95% CI −6 to 18]), IDF (2% [−9 to 14]), or Harmonized (−0.2% [−11 to 11]) definitions. Results were markedly similar when subgroup-specific cut points were used.
All metabolic syndrome definitions were associated with an increased HR for incident CVD in multivariable-adjusted analyses (1.7 [95% CI 1.6–1.9], 1.8 [1.6–2.0], and 1.9 [1.7–2.0] for ATP III, IDF, and Harmonized, respectively, and 1.7 [1.6–1.9] and 1.8 [1.6–1.9] for the empirically derived uniform and subgroup-specific cut point definitions, respectively). Results were similar among individuals without hypertension or diabetes or when the HRs were adjusted for antihypertensive and lipid-lowering medication use. A fivefold cross-validation study resulted in identical cut points and similar performance characteristics.