Objective: The presence of insulin resistance and the metabolic syndrome are known risk markers for macrovascular disease in patients with and without type 2 diabetes. This study has examined whether these also were predictors of micro- and macrovascular complications in type 1 diabetic patients participating in the Diabetes Control and Complications Trial (DCCT).
Research design and methods: International Diabetes Federation (IDF) criteria were used to identify the metabolic syndrome in 1,337 Caucasian DCCT patients at baseline. Insulin resistance was calculated using their estimated glucose disposal rate (eGDR). Insulin dose (units/kg) was also used as a separate marker of insulin resistance.
Results: The eGDR (but not insulin dose or metabolic syndrome) at baseline strongly predicted the development of retinopathy, nephropathy, and cardiovascular disease (hazard ratios 0.75, 0.88, and 0.70, respectively, per mg x kg(-1) x min(-1) change; P < 0.001, P = 0.005, and P = 0.002, respectively). Through mainly weight gain, the prevalence of the metabolic syndrome increased steadily from baseline to year 9 in conventionally treated (from 15.5 to 27.2%) and especially in the intensively treated (from 13.7 to 45.4%) patients.
Conclusions: Higher insulin resistance at baseline in the DCCT (as estimated by eGDR) was associated with increased subsequent risk of both micro- and macrovascular complications. Insulin dose and the presence of IDF-defined metabolic syndrome were poor predictors by comparison. Although intensive treatment was associated with a higher subsequent prevalence of metabolic syndrome, the benefits of improved glycemia appear to outweigh the risks related to development of the metabolic syndrome.