The use of different definitions of the metabolic syndrome has led to inconsistent results on the association between the metabolic syndrome and risk of cardiovascular disease. We examined the association between the metabolic syndrome and risk of cardiovascular disease.

A MEDLINE search (1966-April 2005) was conducted to identify prospective studies that examined the association between the metabolic syndrome and risk of cardiovascular disease. Information on sample size, participant characteristics, metabolic syndrome definition, follow-up duration, and endpoint assessment was abstracted.

Data from 21 studies met the inclusion criteria and were included. Individuals with the metabolic syndrome, compared to those without, had an increased mortality from all causes (relative risk [RR] 1.35; 95% confidence interval [CI], 1.17-1.56) and cardiovascular disease (RR 1.74; 95% CI, 1.29-2.35); as well as an increased incidence of cardiovascular disease (RR 1.53; 95% CI, 1.26-1.87), coronary heart disease (RR 1.52; 95% CI, 1.37-1.69) and stroke (RR 1.76; 95% CI, 1.37-2.25). The relative risk of cardiovascular disease associated with the metabolic syndrome was higher in women compared with men and higher in studies that used the World Health Organization definition compared with studies that used the Adult Treatment Panel III definition.

This analysis strongly suggests that the metabolic syndrome is an important risk factor for cardiovascular disease incidence and mortality, as well as all-cause mortality. The detection, prevention, and treatment of the underlying risk factors of the metabolic syndrome should become an important approach for the reduction of the cardiovascular disease burden in the general population.