Wisconsin Epidemiological Study of Cardiovascular Disease in Type 1 Diabetes

BACKGROUND:

With recent advances in diabetes treatment, especially the evidence that tight control of glycemia, diminishes glycemia related complications it is becoming apparent that the main barriers to further increases in the longevity of patients with insulin-dependent (type 1) diabetes mellitus are the long-term cardiovascular complications of this condition. However, development of effective strategies to prevent cardiovascular complications of diabetes have been impeded by uncertainty as to the relative importance in their pathogenesis of hyperglycemia, early renal dysfunction or excess levels of conventional risk factors. In this context, research to elucidate the predictors of cardiovascular complications of diabetes in well-characterized populations followed long term has the potential to be of considerable clinical and public health importance.

DESIGN NARRATIVE:

The study was a population-based, longitudinal, cohort study to determine the prevalence and incidence rates of cardiovascular disease morbidity and mortality in people with Type 1 diabetes of long duration. The mean age of the cohort and the long duration of diabetes provided an opportunity to document the prevalence and incidence of coronary heart disease, myocardial infarction, angina, congestive heart failure, stroke, transient ischemic attacks, peripheral vascular disease and cardiovascular disease mortality in a large population-base group of persons with Type 1 diabetes. Standardized protocols for exams and interviews were used during the baseline, 4-, 10-, and 14-year follow-up exams. Retinal photographs of each study participant were taken at the baseline examination. This permitted the investigators to test the predictive ability of focal and generalized retinal arteriolar narrowing and arteriovenous crossing changes (i.e., A/V nicking) for subsequent macrovascular events controlling for other risk factors. These factors included blood pressure, cigarette smoking, serum lipids, body mass index, duration of diabetes, and glycemia.

The cohort was re-examined to obtain ECGs, blood lipid fractions not previously measured, and fibrinogen, as well as upper and lower extremity blood pressures, urine specimens, and medical records. This provided information about silent infarctions and other cardiographic abnormalities as well as previously doctor-diagnosed macrovascular events in long-term survivors of Type 1 diabetes. Study examinations were performed in a mobile van. Participants provided two urine specimens for determination of urinary albumin excretion. Fasting blood was obtained for determination of glycosylated hemoglobin A1c, blood sugar, serum cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, LDL particle size, serum creatinine, and fibrinogen. Additional study procedures included measurements of weight and height, waist and hip girth, and brachial and ankle blood pressures. Electrocardiography was also performed. A questionnaire was administered. Participants were subsequently interviewed yearly and clinical and hospital records and death certificates were collected to document new cardiovascular disease events.