Diabetes mellitus and macrovascular complications. An epidemiological perspective

It is clearly recognized that patients with NIDDM have an increased risk for CHD. Recent data indicate that persons with glucose concentrations in the nondiabetic range also may be at higher risk for CHD. These associations may not represent cause and effect, however. Emerging data suggest that hyperglycemia and CHD may both arise from hyperinsulinemia/insulin resistance. In support of this hypothesis are studies showing that NIDDM and CHD have many risk factors in common, including age, elevated blood pressure, dyslipidemia, adiposity, and a central pattern of fat distribution. Moreover, these risk factors are frequent concomitants of hyperinsulinemia, itself a risk factor for CHD and perhaps for NIDDM. Although the duration of NIDDM has been infrequently related to risk of CHD, the authors hypothesize that duration of hyperinsulinemia/insulin resistance would be a more sensitive marker for risk of CHD. The relation of IDDM to CHD is a different situation. The etiological process leading to IDDM, namely the destruction of beta-cells in genetically predisposed persons, is not related to cardiovascular risk. However, IDDM patients still have an excess of CVD, the risk factors for which may vary according to the location of the diseases (e.g., LEAD vs. CHD). There is a strong relationship between proteinuria and CVD, which has led to a general theory of vascular complications in IDDM based on defective heparan sulfate metabolism (Steno hypothesis). Recent evidence challenges parts of this hypothesis, and the possibility is raised that a higher case-fatality rate in a subgroup of patients with both renal and CVD explains part of the renal connection, as does the general worsening of CVD risk factors.