Is prediction of cardiovascular disease and all-cause mortality genuinely driven by the metabolic syndrome, and independently from its component variables? The Dubbo study.

BACKGROUND: The Metabolic Syndrome (MetS) predicts an increased risk of cardiovascular disease and all-cause mortality. Is this prediction genuinely driven by the syndrome and independently from its component variables?
METHODS: A longitudinal cohort study in Dubbo, Australia of 2805 men and women ≥60 years followed for 16 years from 1988. Cox proportional hazards models were calculated for coronary heart disease (CHD), ischaemic stroke and all-cause mortality with MetS as an independent variable. Separate models included the MetS variable, with or without the presence of one of its five component variables.
RESULTS: MetS was present in 33% of subjects. Obesity was present in 43% of those with MetS, high blood pressure in 99%, elevated triglycerides in 83%, low HDL-C in 75% and glycaemia in 48%. With respect to CHD and all-cause mortality, prediction by MetS was similar in the presence or absence of individual component factors (e.g. hazard ratio (95% CI) for CHD by MetS when low HDL-C present 1.60(1.39-1.84) and 1.67(1.37-2.04) when low HDL-C absent). With stroke, prediction by MetS was lost in the absence of elevated triglycerides or glycaemia factors (e.g. hazard ratio for stroke by MetS when glycaemia present 1.59(1.24-2.05) and 1.08(0.82-1.42) when glycaemia absent).
CONCLUSIONS: The findings suggest that prediction of CHD and all-cause mortality is genuinely driven by the MetS and independently of its component variables. Prediction of ischaemic stroke is more complex, with some components providing prediction independently from the MetS.