Quarterly Focus Issue: Prevention/Outcome
Clinical Research: Metabolic Syndrome
The Metabolic Syndrome and Cardiovascular Risk: A Systematic Review and Meta-Analysis

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Objectives

We sought to conduct a systematic review and meta-analysis of the cardiovascular risk associated with the metabolic syndrome as defined by the 2001 National Cholesterol Education Program (NCEP) and 2004 revised National Cholesterol Education Program (rNCEP) definitions.

Background

Numerous studies have investigated the cardiovascular risk associated with the NCEP and rNCEP definitions of the metabolic syndrome. There is debate regarding the prognostic significance of the metabolic syndrome for cardiovascular outcomes.

Methods

We searched the Cochrane Library, EMBASE, and Medline databases through June 2009 for prospective observational studies investigating the cardiovascular effects of the metabolic syndrome. Two reviewers extracted data, which were aggregated using random-effects models.

Results

We identified 87 studies, which included 951,083 patients (NCEP: 63 studies, 497,651 patients; rNCEP: 33 studies, 453,432 patients). There was little variation between the cardiovascular risk associated with NCEP and rNCEP definitions. When both definitions were pooled, the metabolic syndrome was associated with an increased risk of cardiovascular disease (CVD) (relative risk [RR]: 2.35; 95% confidence interval [CI]: 2.02 to 2.73), CVD mortality (RR: 2.40; 95% CI: 1.87 to 3.08), all-cause mortality (RR: 1.58; 95% CI: 1.39 to 1.78), myocardial infarction (RR: 1.99; 95% CI: 1.61 to 2.46), and stroke (RR: 2.27; 95% CI: 1.80 to 2.85). Patients with the metabolic syndrome, but without diabetes, maintained a high cardiovascular risk.

Conclusions

The metabolic syndrome is associated with a 2-fold increase in cardiovascular outcomes and a 1.5-fold increase in all-cause mortality. Studies are needed to investigate whether or not the prognostic significance of the metabolic syndrome exceeds the risk associated with the sum of its individual components. Furthermore, studies are needed to elucidate the mechanisms by which the metabolic syndrome increases cardiovascular risk.

Key Words

cardiovascular disease
cardiovascular risk
meta-analysis
metabolic syndrome
mortality
National Cholesterol Education Program

Abbreviations and Acronyms

BMI
body mass index
CI
confidence interval
CVD
cardiovascular disease
HDL
high-density lipoprotein
HR
hazard ratio
LDL
low-density lipoprotein
MI
myocardial infarction
NCEP
National Cholesterol Education Program
rNCEP
revised National Cholesterol Education Program
RR
relative risk

Cited by (0)

This work is supported by the Canadian Institutes of Health Research(CIHR grant number 82918). Mr. Mottillo is supported by a Canadian Cardiovascular Outcomes Research Team (CCORT) summer studentship funded through a CIHR Team Grant in Cardiovascular Outcomes Research. Dr. Genest is on the Speakers' Bureau for Merck and AstraZeneca. Dr. Joseph is a Chercheur-National of the Fonds de la Recherche en Santé du Québec (FRSQ). Dr. Pilote is a Chercheur-National of the FRSQ. Dr. Poirier is a Senior Physician-Scientist of the FRSQ. Dr. Rinfret is a Junior Physician-Scientist of the FRSQ. Dr. Schiffrin holds a Canada Research Chair in Vascular and Hypertension Research. Dr. Eisenberg is a Chercheur-National of the FRSQ. All other authors have reported that they have no relationships to disclose.