The insulin resistance syndrome (syndrome X) and risk factors for coronary heart disease: An epidemiologic overview

Recent research has identified several risk factors for coronary heart disease that cluster with greater frequency than would be expected by chance. These risk factors include obesity and a centralized distribution of body fat, elevated blood pressure, dyslipidemia, and glucose intolerance. An underlying basis for this cluster appears to be disturbances in insulin-mediated glucose homeostasis as reflected by hyperinsu-linemia and/or a resistance to its actions. Whether hyperinsulinemia/insulin resistance is a necessary and sufficient cause of these metabolic derangements is uncertain. Many studies conducted in the United States and abroad among children, adolescents, and adults have reported hyperinsulinemia/insulin resistance to be associated with an adverse coronary risk factor profile. Other studies, conducted primarily in older or noncaucasian adults, have failed to note such relationships. In many instances, multivariate analyses of cross-sectional data designed to address the primacy of insulin resistance in this cluster of risk factors has introduced more confusion than it has resolved. Only prospective studies, particularly those that intervene to “perturb the system,” can adequately address these questions.