Impact of metabolic syndrome on ischemic heart disease - a prospective cohort study in an Iranian adult population: Isfahan Cohort Study.

BACKGROUND The impact of the metabolic syndrome among populations in the Middle East region is unknown; we therefore examined the association between the syndrome and the risk of ischemic heart disease (IHD) in an Iranian population. METHODS AND RESULTS The Isfahan Cohort Study (ICS) prospectively followed 6146 Iranian people (51.8% women, aged 35-75 years) from three cities and their rural districts who were initially free of ischemic heart disease. During the 5 year follow-up, 209 (56% men) cases of ischemic heart disease were detected. The metabolic syndrome was defined by the modified criteria of the National Cholesterol Education Program Adult Treatment Panel III (NCEP/ATPIII). End points were defined as fatal and nonfatal myocardial infarction, sudden cardiac death and unstable angina. A clear dose-response relationship was found between the number of metabolic risk factors and the incidence of IHD, with the hazard ratios increasing dose-dependently from 1.72 (95% CI 0.86-3.46) for only one to 1.97 (1.00-3.90), 2.85 (1.45-5.58) and 4.44 (2.25-8.76) for 2, 3 and ≥4 metabolic syndrome component respectively, relative to those with no component. The adjusted hazard ratio (95% CI) associated with the metabolic syndrome was 1.58 (1.06-2.35) in men and 1.72 (1.08-2.74) in women for IHD. The contribution of metabolic syndrome to the IHD risk was particularly strong among smokers although there was no significant interaction. CONCLUSIONS The metabolic syndrome by NCEP/ATPIII definition is a major determinant of ischemic heart disease in this middle-aged Iranian population, especially among smokers.