During the DCCT, the frequency of cardiovascular events was too low to determine whether the interventions had significantly different effects. During EDIC, two measures of atherosclerosis were employed, ultrasound measurement of carotid intima-media wall thickness (IMT) and electron beam (or multidetector) computed tomography of the heart to measure coronary artery calcification. The progression of IMT during EDIC was decreased in the former intensive therapy group compared with the former conventional therapy group. Similarly, the prevalence of coronary calcification was less in the former intensive treatment group. Both measures were associated with level of glycemia, measured by HbA1c, during the DCCT, independent of other established cardiovascular risk factors. The frequency of major CVD clinical events (defined as any one of the following: fatal and non-fatal myocardial infarctions and stroke, silent myocardial infarctions, angina confirmed by a positive stress test or catheterization, and PTCA or CABG) has increased during EDIC. Preliminary analysis of the clinical events has shown differences between the two DCCT treatment groups that support a benefit of intensive therapy on clinical CVD outcomes, as previously demonstrated for atherosclerosis. Collaboration with the Medical University of South Carolina, supported by an NHLBI Program Project, has explored inflammatory, lipid, and hemorheologic risk factors for micro- and macrovascular disease during EDIC.
The rate of mortality in the DCCT cohort has been low. The number of events has been too small to provide a definitive assessment of the possible effects of the initial intensive versus conventional therapy during DCCT on risk of mortality, or to assess the association of other complications, principally nephropathy, on risk of mortality. However, projections over the next 10 years suggest that an adequate number of deaths are expected to allow an assessment of the effects of previous DCCT therapy, the history of glycemia and emergence of other complications on the risk of mortality.
COLLABORATIONS- The DCCT/EDIC Research Group has sought to amplify the clinical science opportunities afforded by the extensive clinical data collected during DCCT/EDIC. Four important collaborations have extended and expanded our collection of data relevant to CVD.
- Our collaborators at The Medical University of South Carolina (MUSC) have obtained 3 samples of specially preserved plasma at different time points from approximately 1000 EDIC participants for measurement of multiple risk factors, including nuclear magnetic resonance lipoprotein profiles. Many of these assays have already been performed and await correlation analyses with CVD events and their surrogates.
- Our collaborators at University of Washington have received serum from 85-90% of the participants every 2 years throughout the DCCT and EDIC for fractionation of lipoproteins by gradient ultracentrifugation. One of the MUSC collaborators, now at University of Oklahoma, has added characterization of apoproteins important in lipoprotein metabolism.
- In addition to the biochemical data generated by our collaborators at MUSC and the University of Washington, a DCCT/EDIC Genetics Project has been initiated. (A proposal for continuation of the genetics project will be submitted separately). Our collaborators at the Hospital for Sick Children/University of Toronto have received DNA from virtually all the participants and from 2918 first degree relatives, representing 87% of the relatives who were not available and did not refuse to provide their DNA outright (25% of all relatives). Genetic analyses for genes influencing CVD are being conducted by 3 approaches: population based association in the DCCT/EDIC probands with candidate genes; "trios" analysis with probands and their parents and siblings; family based associations with multiplex families in whom relatives have also been previously clinically phenotyped for complications.
- A collaboration with investigators located in several centers, including UCSF, that focuses on urologic and sexual dysfunction in diabetes (Uro-EDIC) has yielded important new insights.
In addition to the major, planned collaborations above, the DCCT/EDIC Research Group has made its phenotypic data and saved samples available to outside investigators for almost a decade. The DCCT/EDIC Research Group is also collaborating with the repositories recently established by NIDDK to share phenotypic data, genetic samples, and other biologic samples, as available, with external investigators.