Components of the “Metabolic Syndrome” and Incidence of Type 2 Diabetes

Components of the “Metabolic Syndrome” and Incidence of Type 2 Diabetes Robert L. Hanson , Giuseppina Imperatore , Peter H. Bennett and William C. Knowler From the Diabetes and Arthritis Epidemiology Section, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona Abstract The combination of insulin resistance, dyslipidemia, hypertension, and obesity has been described as a “metabolic syndrome” that is a strong determinant of type 2 diabetes. Factor analysis was used to identify components of this syndrome in 1,918 Pima Indians. Prospective analyses were conducted to evaluate associations of identified factors with incidence of diabetes. Factor analysis identified 4 factors that accounted for 79% of the variance in the original 10 variables. Each of these factors reflected a proposed component of the metabolic syndrome: insulinemia, body size, blood pressure, and lipid metabolism. Among 890 originally nondiabetic participants with follow-up data, 144 developed diabetes in a median follow-up of 4.1 years. The insulinemia factor was strongly associated with diabetes incidence (incidence rate ratio [IRR] for a 1-SD difference in factor scores = 1.81, P < 0.01). The body size and lipids factors also significantly predicted diabetes (IRR 1.52 and 1.37, respectively, P < 0.01 for both), whereas the blood pressure factor did not (IRR 1.11, P = 0.20). Identification of four unique factors with different associations with incidence of diabetes suggests that the correlations among these variables reflect distinct metabolic processes, about which substantial information may be lost in the attempt to combine them into a single entity. Footnotes Address correspondence to Robert L. Hanson, Diabetes and Arthritis Epidemiology Section, National Institute of Diabetes and Digestive and Kidney Diseases, 1550 E. Indian School Rd., Phoenix, AZ 85014. E-mail: rhanson{at}phx.niddk.nih.gov . Received for publication 9 May 2002 and accepted in revised form 17 July 2002. G.I. is currently affiliated with the Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control, Atlanta, Georgia. G 0 , fasting glucose concentration; G 2 , 2-h plasma glucose concentration; I 0 , fasting insulin concentration; I 2 , 2-h serum insulin concentration; IRR, incidence rate ratio; NCEP, National Cholesterol Education Program; ROC, receiver operating characteristic; WHO, World Health Organization. DIABETE