RISK VARIABLE CLUSTERING IN THE INSULIN-RESISTANCE SYNDROME - THE FRAMINGHAM OFFSPRING STUDY

Insulin resistance has been hypothesized to unify the clustering of hy pertension, glucose intolerance, hyperinsulinemia, increased levels of triglyceride and decreased HDL cholesterol, and central and overall o besity We tested this hypothesis with factor analysis, a statistical t echnique that should identify one factor if a single process underlies the clustering of these risk variables, From 2,458 nondiabetic subjec ts of the Framingham Offspring Study, we collected clinical data, fast ing and 2-h postchallenge glucose and insulin levels, and fasting lipi d levels, We performed factor analyses separately for men and women in the entire population and among subgroups with features of the insuli n resistance syndrome, Subjects ranged in age from 26 to 82 years (mea n age 54); 53% were women, 13.4% had impaired glucose tolerance, 27.6% had hypertension, 40% were obese, and 11.6% mere hyperinsulinemic, de fined by elevated fasting insulin levels. Underlying the clustering of these risk variables were three factors, Fasting and 2-h postchalleng e insulin levels, fasting triglyceride and HDL cholesterol levels, BMI , and waist-to-hip ratio were associated with one factor, Fasting and 2-h levels of glucose and insulin were associated with a second factor , Systolic blood pressure, diastolic blood pressure, and BMI were asso ciated with a third factor, Results were similar for men and women and for all subgroups, These results were consistent with more than one i ndependent physiological process underlying risk variable clustering: a central metabolic syndrome (characterized by hyperinsulinemia, dysli pidemia, and obesity), glucose intolerance, and hypertension. Glucose intolerance and hypertension were linked to the central syndrome throu gh shared correlations with insulin levels and obesity insulin resista nce (reflected by hyperinsulinemia) alone did not appear to underlie a ll features of the insulin resistance syndrome.