Invited commentary: insulin resistance syndrome? Syndrome X? Multiple metabolic syndrome? A syndrome at all? Factor analysis reveals patterns in the fabric of correlated metabolic risk factors.

Factor analysis has emerged as a useful method for understanding patterns underlying the co-occurrence of metabolic risk factors for both type 2 diabetes and atherosclerosis--often referred to as "insulin resistance syndrome." In factor analysis of data on 322 healthy elderly people from the Cardiovascular Health Study, Sakkinen et al. (Am J Epidemiol 2000;152:897-907) confirmed findings from a dozen prior studies that as many as four distinct physiologic domains comprise the syndrome, with a unifying role for markers of insulin resistance. With the addition of markers of hemostasis and inflammation, they also found that impaired fibrinolysis and endothelial dysfunction are central features of the syndrome, while inflammation is only weakly linked to insulin resistance through associations with obesity.