title: Metabolic syndrome and risk of incident cardiovascular events and death: a systematic review and meta-analysis of longitudinal studies.
abstract: OBJECTIVE
  The purpose of this research was to assess the association between the metabolic syndrome (MetSyn) and cardiovascular events and mortality by meta-analyses of longitudinal studies.
  
  
  BACKGROUND
  Controversy exists regarding the cardiovascular risk associated with MetSyn.
  
  
  METHODS
  We searched electronic reference databases through March 2005, studies that referenced Reaven's seminal article, abstracts presented at meetings in 2003 to 2004, and queried experts. Two reviewers independently assessed eligibility. Longitudinal studies reporting associations between MetSyn and cardiovascular events or mortality were eligible. Two reviewers independently used a standardized form to collect data from published reports. Authors were contacted. Study quality was assessed by the control of selection, detection, and attrition biases.
  
  
  RESULTS
  We found 37 eligible studies that included 43 cohorts (inception 1971 to 1997) and 172,573 individuals. Random effects meta-analyses showed MetSyn had a relative risk (RR) of cardiovascular events and death of 1.78 (95% confidence interval [CI] 1.58 to 2.00). The association was stronger in women (RR 2.63 vs. 1.98, p = 0.09), in studies enrolling lower risk (<10%) individuals (RR 1.96 vs. 1.43, p = 0.04), and in studies using factor analysis or the World Health Organization definition (RR 2.68 and 2.06 vs. 1.67 for National Cholesterol Education Program definition and 1.35 for other definitions; p = 0.005). The association remained after adjusting for traditional cardiovascular risk factors (RR 1.54, 95% CI 1.32 to 1.79).
  
  
  CONCLUSIONS
  The best available evidence suggests that people with MetSyn are at increased risk of cardiovascular events. These results can help clinicians counsel patients to consider lifestyle interventions, and should fuel research of other preventive interventions.
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA. gami.apoor@mayo.edu
authors.forename: Apoor S
authors.initials: AS
authors.lastname: Gami
authors.forename: Brandi J
authors.initials: BJ
authors.lastname: Witt
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Howard
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Erwin
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Gami
authors.forename: Virend K
authors.initials: VK
authors.lastname: Somers
authors.forename: Victor M
authors.initials: VM
authors.lastname: Montori
mesh_terms: D002318:Cardiovascular Diseases / Q000209:etiology* / Q000401:mortality*; D006801:Humans; D008137:Longitudinal Studies; D024821:Metabolic Syndrome / Q000150:complications*; D012307:Risk Factors