Are Metabolic Risk Factors One Unified Syndrome? Modeling the Structure of the Metabolic Syndrome X

The metabolic syndrome, manifested by insulin resistance, obesity, dyslipidemia, and hypertension, is conceived to increase the risk for coronary heart disease and type II diabetes. Several studies have used factor analysis to explore its underlying structure among related risk variables but reported different results. Taking a hypothesis-testing approach, this study used confirmatory factor analysis to specify and test the factor structure of the metabolic syndrome. A hierarchical four-factor model, with an overarching metabolic syndrome factor uniting the insulin resistance, obesity, lipid, and blood pressure factors, was proposed and tested with 847 men who participated in the Normative Aging Study between 1987 and 1991. Simultaneous multi-group analyses were also conducted to test the stability of the proposed model across younger and older participants and across individuals with and without cardiovascular disease. The findings demonstrated that the proposed structure was well supported (comparative fit index = 0.97, root mean square error approximation = 0.06) and stable across subgroups. The metabolic syndrome was represented primarily by the insulin resistance and obesity factors, followed by the lipid factor, and, to a lesser extent, the blood pressure factor. This study provides an empirical foundation for conceptualizing and measuring the metabolic syndrome that unites four related components (insulin resistance, obesity, lipids, and blood pressure).